diff --git a/packages/pigeon/CHANGELOG.md b/packages/pigeon/CHANGELOG.md
index 6be42dca77c6..c63fd4685f5c 100644
--- a/packages/pigeon/CHANGELOG.md
+++ b/packages/pigeon/CHANGELOG.md
@@ -5,6 +5,7 @@
 * [front-end] Added more errors for incorrect usage of Pigeon (previously they were just ignored).
 * Moved Pigeon to using a custom codec which allows collection types to contain custom classes.
 * Started allowing primitive data types as arguments and return types.
+* Started supporting generics' type arguments for fields in classes.
 
 ## 0.3.0
 
diff --git a/packages/pigeon/lib/ast.dart b/packages/pigeon/lib/ast.dart
index bfc438fe8de5..b9b316b09e32 100644
--- a/packages/pigeon/lib/ast.dart
+++ b/packages/pigeon/lib/ast.dart
@@ -20,10 +20,8 @@ class Method extends Node {
   Method({
     required this.name,
     required this.returnType,
-    required this.argType,
-    this.isArgNullable = false,
+    required this.arguments,
     this.isAsynchronous = false,
-    this.isReturnNullable = false,
     this.offset,
   });
 
@@ -31,16 +29,10 @@ class Method extends Node {
   String name;
 
   /// The data-type of the return value.
-  String returnType;
-
-  /// True if the method can return a null value.
-  bool isReturnNullable;
+  Field returnType;
 
   /// The data-type of the argument.
-  String argType;
-
-  /// True if the argument has a null tag `?`.
-  bool isArgNullable;
+  List<Field> arguments;
 
   /// Whether the receiver of this method is expected to return synchronously or not.
   bool isAsynchronous;
@@ -50,7 +42,7 @@ class Method extends Node {
 
   @override
   String toString() {
-    return '(Api name:$name returnType:$returnType argType:$argType isAsynchronous:$isAsynchronous)';
+    return '(Method name:$name returnType:$returnType argType:$arguments isAsynchronous:$isAsynchronous)';
   }
 }
 
@@ -82,8 +74,47 @@ class Api extends Node {
   }
 }
 
+/// An entity that represents a typed concept, like a [TypeArgument] or [Field].
+abstract class TypedEntity {
+  /// The data-type of the entity (ex 'String' or 'int').
+  String get dataType;
+
+  /// The type arguments to the entity.
+  List<TypeArgument>? get typeArguments;
+
+  /// True if the type is nullable.
+  bool get isNullable;
+}
+
+/// A parameter to a generic entity.  For example, "String" to "List<String>".
+class TypeArgument implements TypedEntity {
+  /// Constructor for [TypeArgument].
+  TypeArgument({
+    required this.dataType,
+    required this.isNullable,
+    this.typeArguments,
+  });
+
+  /// A string representation of the base datatype.
+  @override
+  final String dataType;
+
+  /// The type arguments to this [TypeArgument].
+  @override
+  final List<TypeArgument>? typeArguments;
+
+  /// True if the type is nullable.
+  @override
+  final bool isNullable;
+
+  @override
+  String toString() {
+    return '(TypeArgument dataType:$dataType isNullable:$isNullable typeArguments:$typeArguments)';
+  }
+}
+
 /// Represents a field on a [Class].
-class Field extends Node {
+class Field extends Node implements TypedEntity {
   /// Parametric constructor for [Field].
   Field({
     required this.name,
@@ -97,20 +128,23 @@ class Field extends Node {
   String name;
 
   /// The data-type of the field (ex 'String' or 'int').
+  @override
   String dataType;
 
   /// The offset in the source file where the field appears.
   int? offset;
 
   /// True if the datatype is nullable (ex `int?`).
+  @override
   bool isNullable;
 
   /// Type parameters used for generics.
-  List<Field>? typeArguments;
+  @override
+  List<TypeArgument>? typeArguments;
 
   @override
   String toString() {
-    return '(Field name:$name dataType:$dataType)';
+    return '(Field name:$name dataType:$dataType typeArguments:$typeArguments)';
   }
 }
 
diff --git a/packages/pigeon/lib/dart_generator.dart b/packages/pigeon/lib/dart_generator.dart
index c2311352b8a4..d544ee33410a 100644
--- a/packages/pigeon/lib/dart_generator.dart
+++ b/packages/pigeon/lib/dart_generator.dart
@@ -92,6 +92,18 @@ void _writeCodec(Indent indent, String codecName, Api api) {
   });
 }
 
+String _makeGenericTypeArguments(TypedEntity entity, String nullTag) {
+  return entity.typeArguments != null
+      ? '${entity.dataType}<${entity.typeArguments!.map((TypeArgument e) => 'Object$nullTag').reduce((String value, String element) => '$value, $element')}>'
+      : _addGenericTypes(entity, nullTag);
+}
+
+String _makeGenericCastCall(TypedEntity entity, String nullTag) {
+  return entity.typeArguments != null
+      ? '.cast<${_flattenTypeArguments(entity.typeArguments!, nullTag)}>()'
+      : '';
+}
+
 void _writeHostApi(DartOptions opt, Indent indent, Api api) {
   assert(api.location == ApiLocation.host);
   final String codecName = _getCodecName(api);
@@ -121,12 +133,12 @@ final BinaryMessenger$nullTag _binaryMessenger;
       }
       String argSignature = '';
       String sendArgument = 'null';
-      if (func.argType != 'void') {
-        argSignature = '${func.argType} arg';
+      if (func.arguments.isNotEmpty) {
+        argSignature = '${_addGenericTypes(func.arguments[0], nullTag)} arg';
         sendArgument = 'arg';
       }
       indent.write(
-        'Future<${func.returnType}> ${func.name}($argSignature) async ',
+        'Future<${_addGenericTypes(func.returnType, nullTag)}> ${func.name}($argSignature) async ',
       );
       indent.scoped('{', '}', () {
         final String channelName = makeChannelName(api, func);
@@ -137,9 +149,12 @@ final BinaryMessenger$nullTag _binaryMessenger;
             '\'$channelName\', codec, binaryMessenger: _binaryMessenger);',
           );
         });
-        final String returnStatement = func.returnType == 'void'
+        final String returnType =
+            _makeGenericTypeArguments(func.returnType, nullTag);
+        final String castCall = _makeGenericCastCall(func.returnType, nullTag);
+        final String returnStatement = func.returnType.dataType == 'void'
             ? '// noop'
-            : 'return (replyMap[\'${Keys.result}\'] as ${func.returnType}$nullTag)$unwrapOperator;';
+            : 'return (replyMap[\'${Keys.result}\'] as $returnType$nullTag)$unwrapOperator$castCall;';
         indent.format('''
 final Map<Object$nullTag, Object$nullTag>$nullTag replyMap =\n\t\tawait channel.send($sendArgument) as Map<Object$nullTag, Object$nullTag>$nullTag;
 if (replyMap == null) {
@@ -181,10 +196,12 @@ void _writeFlutterApi(
     indent.addln('');
     for (final Method func in api.methods) {
       final bool isAsync = func.isAsynchronous;
-      final String returnType =
-          isAsync ? 'Future<${func.returnType}>' : func.returnType;
-      final String argSignature =
-          func.argType == 'void' ? '' : '${func.argType} arg';
+      final String returnType = isAsync
+          ? 'Future<${_addGenericTypes(func.returnType, nullTag)}>'
+          : _addGenericTypes(func.returnType, nullTag);
+      final String argSignature = func.arguments.isEmpty
+          ? ''
+          : '${_addGenericTypes(func.arguments[0], nullTag)} arg';
       indent.writeln('$returnType ${func.name}($argSignature);');
     }
     indent.write('static void setup(${api.name}$nullTag api) ');
@@ -215,19 +232,21 @@ void _writeFlutterApi(
               'channel.$messageHandlerSetter((Object$nullTag message) async ',
             );
             indent.scoped('{', '});', () {
-              final String argType = func.argType;
-              final String returnType = func.returnType;
+              final String returnType =
+                  _addGenericTypes(func.returnType, nullTag);
               final bool isAsync = func.isAsynchronous;
               final String emptyReturnStatement = isMockHandler
                   ? 'return <Object$nullTag, Object$nullTag>{};'
-                  : func.returnType == 'void'
+                  : func.returnType.dataType == 'void'
                       ? 'return;'
                       : 'return null;';
               String call;
-              if (argType == 'void') {
+              if (func.arguments.isEmpty) {
                 indent.writeln('// ignore message');
                 call = 'api.${func.name}()';
               } else {
+                final String argType =
+                    _addGenericTypes(func.arguments[0], nullTag);
                 indent.writeln(
                   'assert(message != null, \'Argument for $channelName was null. Expected $argType.\');',
                 );
@@ -263,17 +282,37 @@ void _writeFlutterApi(
   });
 }
 
-String _addGenericTypes(String dataType, String nullTag) {
-  switch (dataType) {
+/// Converts a [List] of [TypeArgument]s to a comma separated [String] to be
+/// used in Dart code.
+String _flattenTypeArguments(List<TypeArgument> args, String nullTag) {
+  return args
+      .map((TypeArgument arg) => arg.typeArguments == null
+          ? '${arg.dataType}$nullTag'
+          : '${arg.dataType}<${_flattenTypeArguments(arg.typeArguments!, nullTag)}>$nullTag')
+      .reduce((String value, String element) => '$value, $element');
+}
+
+/// Creates the type declaration for use in Dart code from a [Field] making sure
+/// that type arguments are used for primitive generic types.
+String _addGenericTypes(TypedEntity entity, String nullTag) {
+  switch (entity.dataType) {
     case 'List':
-      return 'List<Object$nullTag>$nullTag';
+      return (entity.typeArguments == null)
+          ? 'List<Object$nullTag>'
+          : 'List<${_flattenTypeArguments(entity.typeArguments!, nullTag)}>';
     case 'Map':
-      return 'Map<Object$nullTag, Object$nullTag>$nullTag';
+      return (entity.typeArguments == null)
+          ? 'Map<Object$nullTag, Object$nullTag>'
+          : 'Map<${_flattenTypeArguments(entity.typeArguments!, nullTag)}>';
     default:
-      return '$dataType$nullTag';
+      return entity.dataType;
   }
 }
 
+String _addGenericTypesNullable(Field field, String nullTag) {
+  return '${_addGenericTypes(field, nullTag)}$nullTag';
+}
+
 /// Generates Dart source code for the given AST represented by [root],
 /// outputting the code to [sink].
 void generateDart(DartOptions opt, Root root, StringSink sink) {
@@ -315,7 +354,7 @@ void generateDart(DartOptions opt, Root root, StringSink sink) {
     indent.write('class ${klass.name} ');
     indent.scoped('{', '}', () {
       for (final Field field in klass.fields) {
-        final String datatype = _addGenericTypes(field.dataType, nullTag);
+        final String datatype = _addGenericTypesNullable(field, nullTag);
         indent.writeln('$datatype ${field.name};');
       }
       if (klass.fields.isNotEmpty) {
@@ -365,9 +404,16 @@ pigeonMap['${field.name}'] != null
 pigeonMap['${field.name}'] != null
 \t\t? ${field.dataType}.values[pigeonMap['${field.name}']$unwrapOperator as int]
 \t\t: null''', leadingSpace: false, trailingNewline: false);
+            } else if (field.typeArguments != null) {
+              final String genericType =
+                  _makeGenericTypeArguments(field, nullTag);
+              final String castCall = _makeGenericCastCall(field, nullTag);
+              indent.add(
+                '(pigeonMap[\'${field.name}\'] as $genericType$nullTag)$nullTag$castCall',
+              );
             } else {
               indent.add(
-                'pigeonMap[\'${field.name}\'] as ${_addGenericTypes(field.dataType, nullTag)}',
+                'pigeonMap[\'${field.name}\'] as ${_addGenericTypesNullable(field, nullTag)}',
               );
             }
             indent.addln(index == klass.fields.length - 1 ? ';' : '');
diff --git a/packages/pigeon/lib/generator_tools.dart b/packages/pigeon/lib/generator_tools.dart
index 560bcd184fbd..e2b391757439 100644
--- a/packages/pigeon/lib/generator_tools.dart
+++ b/packages/pigeon/lib/generator_tools.dart
@@ -159,9 +159,9 @@ class HostDatatype {
 /// `builtinResolver` will return the host datatype for the Dart datatype for
 /// builtin types.  `customResolver` can modify the datatype of custom types.
 HostDatatype getHostDatatype(Field field, List<Class> classes, List<Enum> enums,
-    String? Function(String) builtinResolver,
+    String? Function(Field) builtinResolver,
     {String Function(String)? customResolver}) {
-  final String? datatype = builtinResolver(field.dataType);
+  final String? datatype = builtinResolver(field);
   if (datatype == null) {
     if (classes.map((Class x) => x.name).contains(field.dataType)) {
       final String customName = customResolver != null
@@ -285,8 +285,10 @@ const int _minimumCodecFieldKey = 128;
 Iterable<EnumeratedClass> getCodecClasses(Api api) sync* {
   final Set<String> names = <String>{};
   for (final Method method in api.methods) {
-    names.add(method.returnType);
-    names.add(method.argType);
+    names.add(method.returnType.dataType);
+    if (method.arguments.isNotEmpty) {
+      names.add(method.arguments[0].dataType);
+    }
   }
   final List<String> sortedNames = names
       .where((String element) =>
diff --git a/packages/pigeon/lib/java_generator.dart b/packages/pigeon/lib/java_generator.dart
index eae2cea23567..88bffad05e01 100644
--- a/packages/pigeon/lib/java_generator.dart
+++ b/packages/pigeon/lib/java_generator.dart
@@ -5,19 +5,6 @@
 import 'ast.dart';
 import 'generator_tools.dart';
 
-const Map<String, String> _javaTypeForDartTypeMap = <String, String>{
-  'bool': 'Boolean',
-  'int': 'Long',
-  'String': 'String',
-  'double': 'Double',
-  'Uint8List': 'byte[]',
-  'Int32List': 'int[]',
-  'Int64List': 'long[]',
-  'Float64List': 'double[]',
-  'List': 'List<Object>',
-  'Map': 'Map<Object, Object>',
-};
-
 /// Options that control how Java code will be generated.
 class JavaOptions {
   /// Creates a [JavaOptions] object
@@ -113,22 +100,6 @@ void _writeCodec(Indent indent, Api api) {
   });
 }
 
-/// This performs Dart to Java type conversions.  If performs a passthrough of
-/// the input if it can't be converted.
-// TODO(gaaclarke): Remove this method and unify it with `_javaTypeForDartType`.
-String _javaTypeForDartTypePassthrough(String type) {
-  const Map<String, String> map = <String, String>{
-    'int': 'Integer',
-    'bool': 'Boolean',
-    'double': 'Double',
-    'Int32List': 'int[]',
-    'Uint8List': 'byte[]',
-    'Int64List': 'long[]',
-    'Float64List': 'double[]',
-  };
-  return map[type] ?? type;
-}
-
 void _writeHostApi(Indent indent, Api api) {
   assert(api.location == ApiLocation.host);
 
@@ -137,17 +108,21 @@ void _writeHostApi(Indent indent, Api api) {
   indent.write('public interface ${api.name} ');
   indent.scoped('{', '}', () {
     for (final Method method in api.methods) {
-      final String argType = _javaTypeForDartTypePassthrough(method.argType);
       final String returnType = method.isAsynchronous
           ? 'void'
-          : _javaTypeForDartTypePassthrough(method.returnType);
+          : _javaTypeForDartType(method.returnType) ??
+              method.returnType.dataType;
       final List<String> argSignature = <String>[];
-      if (method.argType != 'void') {
+      if (method.arguments.isNotEmpty) {
+        final String argType = _javaTypeForDartType(method.arguments[0]) ??
+            method.arguments[0].dataType;
         argSignature.add('$argType arg');
       }
       if (method.isAsynchronous) {
-        final String returnType =
-            method.returnType == 'void' ? 'Void' : method.returnType;
+        final String returnType = method.returnType.dataType == 'void'
+            ? 'Void'
+            : _javaTypeForDartType(method.returnType) ??
+                method.returnType.dataType;
         argSignature.add('Result<$returnType> result');
       }
       indent.writeln('$returnType ${method.name}(${argSignature.join(', ')});');
@@ -180,15 +155,17 @@ static MessageCodec<Object> getCodec() {
           indent.scoped('{', '} else {', () {
             indent.write('channel.setMessageHandler((message, reply) -> ');
             indent.scoped('{', '});', () {
-              final String argType =
-                  _javaTypeForDartTypePassthrough(method.argType);
               final String returnType =
-                  _javaTypeForDartTypePassthrough(method.returnType);
+                  _javaTypeForDartType(method.returnType) ??
+                      method.returnType.dataType;
               indent.writeln('Map<String, Object> wrapped = new HashMap<>();');
               indent.write('try ');
               indent.scoped('{', '}', () {
                 final List<String> methodArgument = <String>[];
-                if (argType != 'void') {
+                if (method.arguments.isNotEmpty) {
+                  final String argType =
+                      _javaTypeForDartType(method.arguments[0]) ??
+                          method.arguments[0].dataType;
                   indent.writeln('@SuppressWarnings("ConstantConditions")');
                   indent.writeln('$argType input = ($argType)message;');
                   indent.write('if (input == null) ');
@@ -200,7 +177,7 @@ static MessageCodec<Object> getCodec() {
                 }
                 if (method.isAsynchronous) {
                   final String resultValue =
-                      method.returnType == 'void' ? 'null' : 'result';
+                      method.returnType.dataType == 'void' ? 'null' : 'result';
                   methodArgument.add(
                     'result -> { '
                     'wrapped.put("${Keys.result}", $resultValue); '
@@ -212,7 +189,7 @@ static MessageCodec<Object> getCodec() {
                     'api.${method.name}(${methodArgument.join(', ')})';
                 if (method.isAsynchronous) {
                   indent.writeln('$call;');
-                } else if (method.returnType == 'void') {
+                } else if (method.returnType.dataType == 'void') {
                   indent.writeln('$call;');
                   indent.writeln('wrapped.put("${Keys.result}", null);');
                 } else {
@@ -265,15 +242,16 @@ static MessageCodec<Object> getCodec() {
 ''');
     for (final Method func in api.methods) {
       final String channelName = makeChannelName(api, func);
-      final String returnType = func.returnType == 'void'
+      final String returnType = func.returnType.dataType == 'void'
           ? 'Void'
-          : _javaTypeForDartTypePassthrough(func.returnType);
-      final String argType = _javaTypeForDartTypePassthrough(func.argType);
+          : _javaTypeForDartType(func.returnType) ?? func.returnType.dataType;
       String sendArgument;
-      if (func.argType == 'void') {
+      if (func.arguments.isEmpty) {
         indent.write('public void ${func.name}(Reply<$returnType> callback) ');
         sendArgument = 'null';
       } else {
+        final String argType = _javaTypeForDartType(func.arguments[0]) ??
+            func.arguments[0].dataType;
         indent.write(
             'public void ${func.name}($argType argInput, Reply<$returnType> callback) ');
         sendArgument = 'argInput';
@@ -288,7 +266,7 @@ static MessageCodec<Object> getCodec() {
         indent.dec();
         indent.write('channel.send($sendArgument, channelReply -> ');
         indent.scoped('{', '});', () {
-          if (func.returnType == 'void') {
+          if (func.returnType.dataType == 'void') {
             indent.writeln('callback.reply(null);');
           } else {
             indent.writeln('@SuppressWarnings("ConstantConditions")');
@@ -313,8 +291,37 @@ String _makeSetter(Field field) {
   return 'set$uppercased';
 }
 
-String? _javaTypeForDartType(String datatype) {
-  return _javaTypeForDartTypeMap[datatype];
+/// Converts a [List] of [TypeArgument]s to a comma separated [String] to be
+/// used in Java code.
+String _flattenTypeArguments(List<TypeArgument> args) {
+  return args
+      .map((TypeArgument e) => _javaTypeForDartType(e) ?? e.dataType)
+      .reduce((String value, String element) => '$value, $element');
+}
+
+String? _javaTypeForDartType(TypedEntity field) {
+  const Map<String, String> javaTypeForDartTypeMap = <String, String>{
+    'bool': 'Boolean',
+    'int': 'Long',
+    'String': 'String',
+    'double': 'Double',
+    'Uint8List': 'byte[]',
+    'Int32List': 'int[]',
+    'Int64List': 'long[]',
+    'Float64List': 'double[]',
+    'Map': 'Map<Object, Object>',
+  };
+  if (javaTypeForDartTypeMap.containsKey(field.dataType)) {
+    return javaTypeForDartTypeMap[field.dataType];
+  } else if (field.dataType == 'List') {
+    if (field.typeArguments == null) {
+      return 'List<Object>';
+    } else {
+      return 'List<${_flattenTypeArguments(field.typeArguments!)}>';
+    }
+  } else {
+    return null;
+  }
 }
 
 String _castObject(
diff --git a/packages/pigeon/lib/java_generator.dart.orig b/packages/pigeon/lib/java_generator.dart.orig
new file mode 100644
index 000000000000..f49900e9dfa9
--- /dev/null
+++ b/packages/pigeon/lib/java_generator.dart.orig
@@ -0,0 +1,486 @@
+// Copyright 2013 The Flutter Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+import 'ast.dart';
+import 'generator_tools.dart';
+
+/// Options that control how Java code will be generated.
+class JavaOptions {
+  /// Creates a [JavaOptions] object
+  const JavaOptions({
+    this.className,
+    this.package,
+    this.copyrightHeader,
+  });
+
+  /// The name of the class that will house all the generated classes.
+  final String? className;
+
+  /// The package where the generated class will live.
+  final String? package;
+
+  /// A copyright header that will get prepended to generated code.
+  final Iterable<String>? copyrightHeader;
+
+  /// Creates a [JavaOptions] from a Map representation where:
+  /// `x = JavaOptions.fromMap(x.toMap())`.
+  static JavaOptions fromMap(Map<String, Object> map) {
+    return JavaOptions(
+      className: map['className'] as String?,
+      package: map['package'] as String?,
+      copyrightHeader: map['copyrightHeader'] as Iterable<String>?,
+    );
+  }
+
+  /// Converts a [JavaOptions] to a Map representation where:
+  /// `x = JavaOptions.fromMap(x.toMap())`.
+  Map<String, Object> toMap() {
+    final Map<String, Object> result = <String, Object>{
+      if (className != null) 'className': className!,
+      if (package != null) 'package': package!,
+      if (copyrightHeader != null) 'copyrightHeader': copyrightHeader!,
+    };
+    return result;
+  }
+
+  /// Overrides any non-null parameters from [options] into this to make a new
+  /// [JavaOptions].
+  JavaOptions merge(JavaOptions options) {
+    return JavaOptions.fromMap(mergeMaps(toMap(), options.toMap()));
+  }
+}
+
+String _getCodecName(Api api) => '${api.name}Codec';
+
+void _writeCodec(Indent indent, Api api) {
+  final String codecName = _getCodecName(api);
+  indent.write('private static class $codecName extends StandardMessageCodec ');
+  indent.scoped('{', '}', () {
+    indent
+        .writeln('public static final $codecName INSTANCE = new $codecName();');
+    indent.writeln('private $codecName() {}');
+    if (getCodecClasses(api).isNotEmpty) {
+      indent.writeln('@Override');
+      indent.write(
+          'protected Object readValueOfType(byte type, ByteBuffer buffer) ');
+      indent.scoped('{', '}', () {
+        indent.write('switch (type) ');
+        indent.scoped('{', '}', () {
+          for (final EnumeratedClass customClass in getCodecClasses(api)) {
+            indent.write('case (byte)${customClass.enumeration}: ');
+            indent.writeScoped('', '', () {
+              indent.writeln(
+                  'return ${customClass.name}.fromMap((Map<String, Object>) readValue(buffer));');
+            });
+          }
+          indent.write('default:');
+          indent.writeScoped('', '', () {
+            indent.writeln('return super.readValueOfType(type, buffer);');
+          });
+        });
+      });
+      indent.writeln('@Override');
+      indent.write(
+          'protected void writeValue(ByteArrayOutputStream stream, Object value) ');
+      indent.writeScoped('{', '}', () {
+        for (final EnumeratedClass customClass in getCodecClasses(api)) {
+          indent.write('if (value instanceof ${customClass.name}) ');
+          indent.scoped('{', '} else ', () {
+            indent.writeln('stream.write(${customClass.enumeration});');
+            indent.writeln(
+                'writeValue(stream, ((${customClass.name}) value).toMap());');
+          });
+        }
+        indent.scoped('{', '}', () {
+          indent.writeln('super.writeValue(stream, value);');
+        });
+      });
+    }
+  });
+}
+
+String _boxedType(String type) {
+  const Map<String, String> map = <String, String>{
+    'int': 'Integer',
+    'bool': 'Boolean',
+    'double': 'Double',
+    'Int32List': 'int[]',
+    'Uint8List': 'byte[]',
+    'Int64List': 'long[]',
+    'Float64List': 'double[]',
+  };
+  return map[type] ?? type;
+}
+
+void _writeHostApi(Indent indent, Api api) {
+  assert(api.location == ApiLocation.host);
+
+  indent.writeln(
+      '/** Generated interface from Pigeon that represents a handler of messages from Flutter.*/');
+  indent.write('public interface ${api.name} ');
+  indent.scoped('{', '}', () {
+    for (final Method method in api.methods) {
+      final String returnType = method.isAsynchronous
+          ? 'void'
+          : _boxedType(method.returnType.dataType);
+      final List<String> argSignature = <String>[];
+      if (method.arguments.isNotEmpty) {
+        final String argType = _boxedType(method.arguments[0].dataType);
+        argSignature.add('$argType arg');
+      }
+      if (method.isAsynchronous) {
+        final String returnType = method.returnType.dataType == 'void'
+            ? 'Void'
+            : method.returnType.dataType;
+        argSignature.add('Result<$returnType> result');
+      }
+      indent.writeln('$returnType ${method.name}(${argSignature.join(', ')});');
+    }
+    indent.addln('');
+    final String codecName = _getCodecName(api);
+    indent.format('''
+/** The codec used by ${api.name}. */
+static MessageCodec<Object> getCodec() {
+\treturn $codecName.INSTANCE;
+}
+''');
+    indent.writeln(
+        '/** Sets up an instance of `${api.name}` to handle messages through the `binaryMessenger`. */');
+    indent.write(
+        'static void setup(BinaryMessenger binaryMessenger, ${api.name} api) ');
+    indent.scoped('{', '}', () {
+      for (final Method method in api.methods) {
+        final String channelName = makeChannelName(api, method);
+        indent.write('');
+        indent.scoped('{', '}', () {
+          indent.writeln('BasicMessageChannel<Object> channel =');
+          indent.inc();
+          indent.inc();
+          indent.writeln(
+              'new BasicMessageChannel<>(binaryMessenger, "$channelName", getCodec());');
+          indent.dec();
+          indent.dec();
+          indent.write('if (api != null) ');
+          indent.scoped('{', '} else {', () {
+            indent.write('channel.setMessageHandler((message, reply) -> ');
+            indent.scoped('{', '});', () {
+              final String returnType = _boxedType(method.returnType.dataType);
+              indent.writeln('Map<String, Object> wrapped = new HashMap<>();');
+              indent.write('try ');
+              indent.scoped('{', '}', () {
+                final List<String> methodArgument = <String>[];
+                if (method.arguments.isNotEmpty) {
+                  final String argType = _boxedType(method.arguments[0].dataType);
+                  indent.writeln('@SuppressWarnings("ConstantConditions")');
+                  indent.writeln('$argType input = ($argType)message;');
+                  indent.write('if (input == null) ');
+                  indent.scoped('{', '}', () {
+                    indent.writeln(
+                        'throw new NullPointerException("Message unexpectedly null.");');
+                  });
+                  methodArgument.add('input');
+                }
+                if (method.isAsynchronous) {
+                  final String resultValue =
+                      method.returnType.dataType == 'void' ? 'null' : 'result';
+                  methodArgument.add(
+                    'result -> { '
+                    'wrapped.put("${Keys.result}", $resultValue); '
+                    'reply.reply(wrapped); '
+                    '}',
+                  );
+                }
+                final String call =
+                    'api.${method.name}(${methodArgument.join(', ')})';
+                if (method.isAsynchronous) {
+                  indent.writeln('$call;');
+                } else if (method.returnType.dataType == 'void') {
+                  indent.writeln('$call;');
+                  indent.writeln('wrapped.put("${Keys.result}", null);');
+                } else {
+                  indent.writeln('$returnType output = $call;');
+                  indent.writeln('wrapped.put("${Keys.result}", output);');
+                }
+              });
+              indent.write('catch (Error | RuntimeException exception) ');
+              indent.scoped('{', '}', () {
+                indent.writeln(
+                    'wrapped.put("${Keys.error}", wrapError(exception));');
+                if (method.isAsynchronous) {
+                  indent.writeln('reply.reply(wrapped);');
+                }
+              });
+              if (!method.isAsynchronous) {
+                indent.writeln('reply.reply(wrapped);');
+              }
+            });
+          });
+          indent.scoped(null, '}', () {
+            indent.writeln('channel.setMessageHandler(null);');
+          });
+        });
+      }
+    });
+  });
+}
+
+void _writeFlutterApi(Indent indent, Api api) {
+  assert(api.location == ApiLocation.flutter);
+  indent.writeln(
+      '/** Generated class from Pigeon that represents Flutter messages that can be called from Java.*/');
+  indent.write('public static class ${api.name} ');
+  indent.scoped('{', '}', () {
+    indent.writeln('private final BinaryMessenger binaryMessenger;');
+    indent.write('public ${api.name}(BinaryMessenger argBinaryMessenger)');
+    indent.scoped('{', '}', () {
+      indent.writeln('this.binaryMessenger = argBinaryMessenger;');
+    });
+    indent.write('public interface Reply<T> ');
+    indent.scoped('{', '}', () {
+      indent.writeln('void reply(T reply);');
+    });
+    final String codecName = _getCodecName(api);
+    indent.format('''
+static MessageCodec<Object> getCodec() {
+\treturn $codecName.INSTANCE;
+}
+''');
+    for (final Method func in api.methods) {
+      final String channelName = makeChannelName(api, func);
+      final String returnType = func.returnType.dataType == 'void'
+          ? 'Void'
+          : _boxedType(func.returnType.dataType);
+      String sendArgument;
+      if (func.arguments.isEmpty) {
+        indent.write('public void ${func.name}(Reply<$returnType> callback) ');
+        sendArgument = 'null';
+      } else {
+        final String argType = _boxedType(func.arguments[0].dataType);
+        indent.write(
+            'public void ${func.name}($argType argInput, Reply<$returnType> callback) ');
+        sendArgument = 'argInput';
+      }
+      indent.scoped('{', '}', () {
+        indent.writeln('BasicMessageChannel<Object> channel =');
+        indent.inc();
+        indent.inc();
+        indent.writeln(
+            'new BasicMessageChannel<>(binaryMessenger, "$channelName", getCodec());');
+        indent.dec();
+        indent.dec();
+        indent.write('channel.send($sendArgument, channelReply -> ');
+        indent.scoped('{', '});', () {
+          if (func.returnType.dataType == 'void') {
+            indent.writeln('callback.reply(null);');
+          } else {
+            indent.writeln('@SuppressWarnings("ConstantConditions")');
+            indent.writeln('$returnType output = ($returnType)channelReply;');
+            indent.writeln('callback.reply(output);');
+          }
+        });
+      });
+    }
+  });
+}
+
+String _makeGetter(Field field) {
+  final String uppercased =
+      field.name.substring(0, 1).toUpperCase() + field.name.substring(1);
+  return 'get$uppercased';
+}
+
+String _makeSetter(Field field) {
+  final String uppercased =
+      field.name.substring(0, 1).toUpperCase() + field.name.substring(1);
+  return 'set$uppercased';
+}
+
+String _flattenTypeArguments(List<TypeArgument> args) {
+  return args
+      .map((TypeArgument e) => e.typeArguments == null
+          ? _boxedType(e.dataType)
+          : '${_boxedType(e.dataType)}<${_flattenTypeArguments(e.typeArguments!)}>')
+      .reduce((String value, String element) => '$value, $element');
+}
+
+String? _javaTypeForDartType(Field field) {
+  const Map<String, String> javaTypeForDartTypeMap = <String, String>{
+    'bool': 'Boolean',
+    'int': 'Long',
+    'String': 'String',
+    'double': 'Double',
+    'Uint8List': 'byte[]',
+    'Int32List': 'int[]',
+    'Int64List': 'long[]',
+    'Float64List': 'double[]',
+    'Map': 'Map<Object, Object>',
+  };
+  if (javaTypeForDartTypeMap.containsKey(field.dataType)) {
+    return javaTypeForDartTypeMap[field.dataType];
+  } else if (field.dataType == 'List') {
+    if (field.typeArguments == null) {
+      return 'List<Object>';
+    } else {
+      return 'List<${_flattenTypeArguments(field.typeArguments!)}>';
+    }
+  } else {
+    return null;
+  }
+}
+
+String _castObject(
+    Field field, List<Class> classes, List<Enum> enums, String varName) {
+  final HostDatatype hostDatatype =
+      getHostDatatype(field, classes, enums, _javaTypeForDartType);
+  if (field.dataType == 'int') {
+    return '($varName == null) ? null : (($varName instanceof Integer) ? (Integer)$varName : (${hostDatatype.datatype})$varName)';
+  } else if (!hostDatatype.isBuiltin &&
+      classes.map((Class x) => x.name).contains(field.dataType)) {
+    return '${hostDatatype.datatype}.fromMap((Map)$varName)';
+  } else {
+    return '(${hostDatatype.datatype})$varName';
+  }
+}
+
+/// Generates the ".java" file for the AST represented by [root] to [sink] with the
+/// provided [options].
+void generateJava(JavaOptions options, Root root, StringSink sink) {
+  final Set<String> rootClassNameSet =
+      root.classes.map((Class x) => x.name).toSet();
+  final Set<String> rootEnumNameSet =
+      root.enums.map((Enum x) => x.name).toSet();
+  final Indent indent = Indent(sink);
+  if (options.copyrightHeader != null) {
+    addLines(indent, options.copyrightHeader!, linePrefix: '// ');
+  }
+  indent.writeln('// $generatedCodeWarning');
+  indent.writeln('// $seeAlsoWarning');
+  indent.addln('');
+  if (options.package != null) {
+    indent.writeln('package ${options.package};');
+  }
+  indent.addln('');
+  indent.writeln('import io.flutter.plugin.common.BasicMessageChannel;');
+  indent.writeln('import io.flutter.plugin.common.BinaryMessenger;');
+  indent.writeln('import io.flutter.plugin.common.MessageCodec;');
+  indent.writeln('import io.flutter.plugin.common.StandardMessageCodec;');
+  indent.writeln('import java.io.ByteArrayOutputStream;');
+  indent.writeln('import java.nio.ByteBuffer;');
+  indent.writeln('import java.util.List;');
+  indent.writeln('import java.util.Map;');
+  indent.writeln('import java.util.HashMap;');
+
+  indent.addln('');
+  indent.writeln('/** Generated class from Pigeon. */');
+  indent.writeln(
+      '@SuppressWarnings({"unused", "unchecked", "CodeBlock2Expr", "RedundantSuppression"})');
+  indent.write('public class ${options.className!} ');
+  indent.scoped('{', '}', () {
+    for (final Enum anEnum in root.enums) {
+      indent.writeln('');
+      indent.write('public enum ${anEnum.name} ');
+      indent.scoped('{', '}', () {
+        int index = 0;
+        for (final String member in anEnum.members) {
+          indent.writeln(
+              '$member($index)${index == anEnum.members.length - 1 ? ';' : ','}');
+          index++;
+        }
+        indent.writeln('');
+        // We use explicit indexing here as use of the ordinal() method is
+        // discouraged. The toMap and fromMap API matches class API to allow
+        // the same code to work with enums and classes, but this
+        // can also be done directly in the host and flutter APIs.
+        indent.writeln('private int index;');
+        indent.write('private ${anEnum.name}(final int index) ');
+        indent.scoped('{', '}', () {
+          indent.writeln('this.index = index;');
+        });
+      });
+    }
+
+    for (final Class klass in root.classes) {
+      indent.addln('');
+      indent.writeln(
+          '/** Generated class from Pigeon that represents data sent in messages. */');
+      indent.write('public static class ${klass.name} ');
+      indent.scoped('{', '}', () {
+        for (final Field field in klass.fields) {
+          final HostDatatype hostDatatype = getHostDatatype(
+              field, root.classes, root.enums, _javaTypeForDartType);
+          indent.writeln('private ${hostDatatype.datatype} ${field.name};');
+          indent.writeln(
+              'public ${hostDatatype.datatype} ${_makeGetter(field)}() { return ${field.name}; }');
+          indent.writeln(
+              'public void ${_makeSetter(field)}(${hostDatatype.datatype} setterArg) { this.${field.name} = setterArg; }');
+          indent.addln('');
+        }
+        indent.write('Map<String, Object> toMap() ');
+        indent.scoped('{', '}', () {
+          indent.writeln('Map<String, Object> toMapResult = new HashMap<>();');
+          for (final Field field in klass.fields) {
+            final HostDatatype hostDatatype = getHostDatatype(
+                field, root.classes, root.enums, _javaTypeForDartType);
+            String toWriteValue = '';
+            if (!hostDatatype.isBuiltin &&
+                rootClassNameSet.contains(field.dataType)) {
+              toWriteValue = '${field.name}.toMap()';
+            } else if (!hostDatatype.isBuiltin &&
+                rootEnumNameSet.contains(field.dataType)) {
+              toWriteValue = '${field.name}.index';
+            } else {
+              toWriteValue = field.name;
+            }
+            indent.writeln('toMapResult.put("${field.name}", $toWriteValue);');
+          }
+          indent.writeln('return toMapResult;');
+        });
+        indent.write('static ${klass.name} fromMap(Map<String, Object> map) ');
+        indent.scoped('{', '}', () {
+          indent.writeln('${klass.name} fromMapResult = new ${klass.name}();');
+          for (final Field field in klass.fields) {
+            indent.writeln('Object ${field.name} = map.get("${field.name}");');
+            if (rootEnumNameSet.contains(field.dataType)) {
+              indent.writeln(
+                  'fromMapResult.${field.name} = ${field.dataType}.values()[(int)${field.name}];');
+            } else {
+              indent.writeln(
+                  'fromMapResult.${field.name} = ${_castObject(field, root.classes, root.enums, field.name)};');
+            }
+          }
+          indent.writeln('return fromMapResult;');
+        });
+      });
+    }
+
+    if (root.apis.any((Api api) =>
+        api.location == ApiLocation.host &&
+        api.methods.any((Method it) => it.isAsynchronous))) {
+      indent.addln('');
+      indent.write('public interface Result<T> ');
+      indent.scoped('{', '}', () {
+        indent.writeln('void success(T result);');
+      });
+    }
+
+    for (final Api api in root.apis) {
+      _writeCodec(indent, api);
+      indent.addln('');
+      if (api.location == ApiLocation.host) {
+        _writeHostApi(indent, api);
+      } else if (api.location == ApiLocation.flutter) {
+        _writeFlutterApi(indent, api);
+      }
+    }
+
+    indent.format('''
+private static Map<String, Object> wrapError(Throwable exception) {
+\tMap<String, Object> errorMap = new HashMap<>();
+\terrorMap.put("${Keys.errorMessage}", exception.toString());
+\terrorMap.put("${Keys.errorCode}", exception.getClass().getSimpleName());
+\terrorMap.put("${Keys.errorDetails}", null);
+\treturn errorMap;
+}''');
+  });
+}
diff --git a/packages/pigeon/lib/objc_generator.dart b/packages/pigeon/lib/objc_generator.dart
index 77612a49854f..d147be3b1fe9 100644
--- a/packages/pigeon/lib/objc_generator.dart
+++ b/packages/pigeon/lib/objc_generator.dart
@@ -79,37 +79,45 @@ const Map<String, String> _objcTypeForDartTypeMap = <String, String>{
   'Map': 'NSDictionary',
 };
 
-const Map<String, String> _propertyTypeForDartTypeMap = <String, String>{
-  'String': 'copy',
-  'bool': 'strong',
-  'int': 'strong',
-  'double': 'strong',
-  'Uint8List': 'strong',
-  'Int32List': 'strong',
-  'Int64List': 'strong',
-  'Float64List': 'strong',
-  'List': 'strong',
-  'Map': 'strong',
-};
+String _flattenTypeArguments(String? classPrefix, List<TypeArgument> args) {
+  final String result = args
+      .map((TypeArgument e) => '${_objcTypeForDartType(classPrefix, e)} *')
+      .reduce((String value, String element) => '$value, $element');
+  return result;
+}
 
-String? _objcTypePtrForPrimitiveDartType(String type) {
-  return _objcTypeForDartTypeMap.containsKey(type)
-      ? '${_objcTypeForDartTypeMap[type]} *'
+String? _objcTypePtrForPrimitiveDartType(String? classPrefix, Field field) {
+  return _objcTypeForDartTypeMap.containsKey(field.dataType)
+      ? '${_objcTypeForDartType(classPrefix, field)} *'
       : null;
 }
 
-/// Returns the objc type for a dart [type], prepending the [classPrefix] for
-/// generated classes.  For example:
-/// _objcTypeForDartType(null, 'int') => 'NSNumber'.
-String _objcTypeForDartType(String? classPrefix, String type) {
-  final String? builtinObjcType = _objcTypeForDartTypeMap[type];
-  return builtinObjcType ?? _className(classPrefix, type);
+String _objcTypeForDartType<T extends TypedEntity>(
+    String? classPrefix, T field) {
+  return _objcTypeForDartTypeMap.containsKey(field.dataType)
+      ? field.typeArguments == null
+          ? _objcTypeForDartTypeMap[field.dataType]!
+          : '${_objcTypeForDartTypeMap[field.dataType]}<${_flattenTypeArguments(classPrefix, field.typeArguments!)}>'
+      : _className(classPrefix, field.dataType);
 }
 
-String _propertyTypeForDartType(String type) {
-  final String? result = _propertyTypeForDartTypeMap[type];
+String _propertyTypeForDartType(Field field) {
+  const Map<String, String> propertyTypeForDartTypeMap = <String, String>{
+    'String': 'copy',
+    'bool': 'strong',
+    'int': 'strong',
+    'double': 'strong',
+    'Uint8List': 'strong',
+    'Int32List': 'strong',
+    'Int64List': 'strong',
+    'Float64List': 'strong',
+    'List': 'strong',
+    'Map': 'strong',
+  };
+
+  final String? result = propertyTypeForDartTypeMap[field.dataType];
   if (result == null) {
-    return 'assign';
+    return 'strong';
   } else {
     return result;
   }
@@ -121,18 +129,16 @@ void _writeClassDeclarations(
   for (final Class klass in classes) {
     indent.writeln('@interface ${_className(prefix, klass.name)} : NSObject');
     for (final Field field in klass.fields) {
-      final HostDatatype hostDatatype = getHostDatatype(
-          field, classes, enums, _objcTypePtrForPrimitiveDartType,
+      final HostDatatype hostDatatype = getHostDatatype(field, classes, enums,
+          (Field x) => _objcTypePtrForPrimitiveDartType(prefix, x),
           customResolver: enumNames.contains(field.dataType)
               ? (String x) => _className(prefix, x)
               : (String x) => '${_className(prefix, x)} *');
       late final String propertyType;
-      if (hostDatatype.isBuiltin) {
-        propertyType = _propertyTypeForDartType(field.dataType);
-      } else if (enumNames.contains(field.dataType)) {
+      if (enumNames.contains(field.dataType)) {
         propertyType = 'assign';
       } else {
-        propertyType = 'strong';
+        propertyType = _propertyTypeForDartType(field);
       }
       final String nullability =
           hostDatatype.datatype.contains('*') ? ', nullable' : '';
@@ -230,36 +236,37 @@ void _writeHostApiDeclaration(Indent indent, Api api, ObjcOptions options) {
     final String returnTypeName =
         _objcTypeForDartType(options.prefix, func.returnType);
     if (func.isAsynchronous) {
-      if (func.returnType == 'void') {
-        if (func.argType == 'void') {
+      if (func.returnType.dataType == 'void') {
+        if (func.arguments.isEmpty) {
           indent.writeln(
               '-(void)${func.name}:(void(^)(FlutterError *_Nullable))completion;');
         } else {
           final String argType =
-              _objcTypeForDartType(options.prefix, func.argType);
+              _objcTypeForDartType(options.prefix, func.arguments[0]);
           indent.writeln(
               '-(void)${func.name}:(nullable $argType *)input completion:(void(^)(FlutterError *_Nullable))completion;');
         }
       } else {
-        if (func.argType == 'void') {
+        if (func.arguments.isEmpty) {
           indent.writeln(
               '-(void)${func.name}:(void(^)($returnTypeName *_Nullable, FlutterError *_Nullable))completion;');
         } else {
           final String argType =
-              _objcTypeForDartType(options.prefix, func.argType);
+              _objcTypeForDartType(options.prefix, func.arguments[0]);
           indent.writeln(
               '-(void)${func.name}:(nullable $argType *)input completion:(void(^)($returnTypeName *_Nullable, FlutterError *_Nullable))completion;');
         }
       }
     } else {
-      final String returnType =
-          func.returnType == 'void' ? 'void' : 'nullable $returnTypeName *';
-      if (func.argType == 'void') {
+      final String returnType = func.returnType.dataType == 'void'
+          ? 'void'
+          : 'nullable $returnTypeName *';
+      if (func.arguments.isEmpty) {
         indent.writeln(
             '-($returnType)${func.name}:(FlutterError *_Nullable *_Nonnull)error;');
       } else {
         final String argType =
-            _objcTypeForDartType(options.prefix, func.argType);
+            _objcTypeForDartType(options.prefix, func.arguments[0]);
         indent.writeln(
             '-($returnType)${func.name}:($argType*)input error:(FlutterError *_Nullable *_Nonnull)error;');
       }
@@ -280,11 +287,13 @@ void _writeFlutterApiDeclaration(Indent indent, Api api, ObjcOptions options) {
   for (final Method func in api.methods) {
     final String returnType =
         _objcTypeForDartType(options.prefix, func.returnType);
-    final String callbackType = _callbackForType(func.returnType, returnType);
-    if (func.argType == 'void') {
+    final String callbackType =
+        _callbackForType(func.returnType.dataType, returnType);
+    if (func.arguments.isEmpty) {
       indent.writeln('- (void)${func.name}:($callbackType)completion;');
     } else {
-      final String argType = _objcTypeForDartType(options.prefix, func.argType);
+      final String argType =
+          _objcTypeForDartType(options.prefix, func.arguments[0]);
       indent.writeln(
           '- (void)${func.name}:($argType*)input completion:($callbackType)completion;');
     }
@@ -403,18 +412,18 @@ void _writeHostApiSource(Indent indent, ObjcOptions options, Api api) {
             final String returnType =
                 _objcTypeForDartType(options.prefix, func.returnType);
             String syncCall;
-            if (func.argType == 'void') {
+            if (func.arguments.isEmpty) {
               syncCall = '[api ${func.name}:&error]';
             } else {
               final String argType =
-                  _objcTypeForDartType(options.prefix, func.argType);
+                  _objcTypeForDartType(options.prefix, func.arguments[0]);
               indent.writeln('$argType *input = message;');
               syncCall = '[api ${func.name}:input error:&error]';
             }
             if (func.isAsynchronous) {
-              if (func.returnType == 'void') {
+              if (func.returnType.dataType == 'void') {
                 const String callback = 'callback(wrapResult(nil, error));';
-                if (func.argType == 'void') {
+                if (func.arguments.isEmpty) {
                   indent.writeScoped(
                       '[api ${func.name}:^(FlutterError *_Nullable error) {',
                       '}];', () {
@@ -429,7 +438,7 @@ void _writeHostApiSource(Indent indent, ObjcOptions options, Api api) {
                 }
               } else {
                 const String callback = 'callback(wrapResult(output, error));';
-                if (func.argType == 'void') {
+                if (func.arguments.isEmpty) {
                   indent.writeScoped(
                       '[api ${func.name}:^($returnType *_Nullable output, FlutterError *_Nullable error) {',
                       '}];', () {
@@ -445,7 +454,7 @@ void _writeHostApiSource(Indent indent, ObjcOptions options, Api api) {
               }
             } else {
               indent.writeln('FlutterError *error;');
-              if (func.returnType == 'void') {
+              if (func.returnType.dataType == 'void') {
                 indent.writeln('$syncCall;');
                 indent.writeln('callback(wrapResult(nil, error));');
               } else {
@@ -487,14 +496,16 @@ void _writeFlutterApiSource(Indent indent, ObjcOptions options, Api api) {
   for (final Method func in api.methods) {
     final String returnType =
         _objcTypeForDartType(options.prefix, func.returnType);
-    final String callbackType = _callbackForType(func.returnType, returnType);
+    final String callbackType =
+        _callbackForType(func.returnType.dataType, returnType);
 
     String sendArgument;
-    if (func.argType == 'void') {
+    if (func.arguments.isEmpty) {
       indent.write('- (void)${func.name}:($callbackType)completion ');
       sendArgument = 'nil';
     } else {
-      final String argType = _objcTypeForDartType(options.prefix, func.argType);
+      final String argType =
+          _objcTypeForDartType(options.prefix, func.arguments[0]);
       indent.write(
           '- (void)${func.name}:($argType*)input completion:($callbackType)completion ');
       sendArgument = 'input';
@@ -512,7 +523,7 @@ void _writeFlutterApiSource(Indent indent, ObjcOptions options, Api api) {
       indent.dec();
       indent.write('[channel sendMessage:$sendArgument reply:^(id reply) ');
       indent.scoped('{', '}];', () {
-        if (func.returnType == 'void') {
+        if (func.returnType.dataType == 'void') {
           indent.writeln('completion(nil);');
         } else {
           indent.writeln('$returnType * output = reply;');
diff --git a/packages/pigeon/lib/pigeon_lib.dart b/packages/pigeon/lib/pigeon_lib.dart
index a1252226f29b..05f86f2f07f9 100644
--- a/packages/pigeon/lib/pigeon_lib.dart
+++ b/packages/pigeon/lib/pigeon_lib.dart
@@ -13,7 +13,8 @@ import 'package:analyzer/dart/analysis/analysis_context_collection.dart'
 import 'package:analyzer/dart/analysis/results.dart' show ParsedUnitResult;
 import 'package:analyzer/dart/analysis/session.dart' show AnalysisSession;
 import 'package:analyzer/dart/ast/ast.dart' as dart_ast;
-import 'package:analyzer/dart/ast/ast.dart' show CompilationUnit;
+import 'package:analyzer/dart/ast/syntactic_entity.dart'
+    as dart_ast_syntactic_entity;
 import 'package:analyzer/dart/ast/visitor.dart' as dart_ast_visitor;
 import 'package:analyzer/error/error.dart' show AnalysisError;
 import 'package:args/args.dart';
@@ -379,12 +380,17 @@ List<Error> _validateAst(Root root, String source) {
   for (final Class klass in root.classes) {
     for (final Field field in klass.fields) {
       if (field.typeArguments != null) {
-        result.add(Error(
-          message:
-              'Unsupported datatype:"${field.dataType}" in class "${klass.name}". Generic fields aren\'t yet supported (https://github.com/flutter/flutter/issues/63468).',
-          lineNumber: _calculateLineNumberNullable(source, field.offset),
-        ));
-      } else if (!(validTypes.contains(field.dataType) ||
+        for (final TypeArgument typeArgument in field.typeArguments!) {
+          if (!typeArgument.isNullable) {
+            result.add(Error(
+              message:
+                  'Generic type arguments must be nullable in field "${field.name}" in class "${klass.name}".',
+              lineNumber: _calculateLineNumberNullable(source, field.offset),
+            ));
+          }
+        }
+      }
+      if (!(validTypes.contains(field.dataType) ||
           customClasses.contains(field.dataType) ||
           customEnums.contains(field.dataType))) {
         result.add(Error(
@@ -397,17 +403,24 @@ List<Error> _validateAst(Root root, String source) {
   }
   for (final Api api in root.apis) {
     for (final Method method in api.methods) {
-      if (method.isReturnNullable) {
+      if (method.returnType.isNullable) {
         result.add(Error(
           message:
-              'Nullable return types types aren\'t supported for Pigeon methods: "${method.argType}" in API: "${api.name}" method: "${method.name}"',
+              'Nullable return types types aren\'t supported for Pigeon methods: "${method.arguments[0].dataType}" in API: "${api.name}" method: "${method.name}"',
           lineNumber: _calculateLineNumberNullable(source, method.offset),
         ));
       }
-      if (method.isArgNullable) {
+      if (method.arguments.length > 1) {
         result.add(Error(
           message:
-              'Nullable argument types aren\'t supported for Pigeon methods: "${method.argType}" in API: "${api.name}" method: "${method.name}"',
+              'Multiple arguments aren\'t yet supported, in API: "${api.name}" method: "${method.name} (https://github.com/flutter/flutter/issues/86971)"',
+          lineNumber: _calculateLineNumberNullable(source, method.offset),
+        ));
+      }
+      if (method.arguments.isNotEmpty && method.arguments[0].isNullable) {
+        result.add(Error(
+          message:
+              'Nullable argument types aren\'t supported for Pigeon methods: "${method.arguments[0].dataType}" in API: "${api.name}" method: "${method.name}"',
           lineNumber: _calculateLineNumberNullable(source, method.offset),
         ));
       }
@@ -462,8 +475,10 @@ class _RootBuilder extends dart_ast_visitor.RecursiveAstVisitor<Object?> {
     final Set<String> referencedTypes = <String>{};
     for (final Api api in _apis) {
       for (final Method method in api.methods) {
-        referencedTypes.add(method.argType);
-        referencedTypes.add(method.returnType);
+        if (method.arguments.isNotEmpty) {
+          referencedTypes.add(method.arguments[0].dataType);
+        }
+        referencedTypes.add(method.returnType.dataType);
       }
     }
 
@@ -613,30 +628,50 @@ class _RootBuilder extends dart_ast_visitor.RecursiveAstVisitor<Object?> {
     return null;
   }
 
+  Field formalParameterToField(dart_ast.FormalParameter parameter) {
+    final dart_ast.TypeName typeName = parameter.childEntities.firstWhere(
+        (dart_ast_syntactic_entity.SyntacticEntity e) =>
+            e is dart_ast.TypeName) as dart_ast.TypeName;
+    final String argType = typeName.name.name;
+    final bool isNullable = typeName.question != null;
+    final List<TypeArgument>? argTypeArguments =
+        typeAnnotationsToTypeArguments(typeName.typeArguments);
+    return Field(
+      dataType: argType,
+      isNullable: isNullable,
+      name: '',
+      typeArguments: argTypeArguments,
+    );
+  }
+
+  static T? getFirstChildOfType<T>(dart_ast.AstNode entity) {
+    for (final dart_ast_syntactic_entity.SyntacticEntity child
+        in entity.childEntities) {
+      if (child is T) {
+        return child as T;
+      }
+    }
+    return null;
+  }
+
   @override
   Object? visitMethodDeclaration(dart_ast.MethodDeclaration node) {
     final dart_ast.FormalParameterList parameters = node.parameters!;
-    late String argType;
-    bool isNullable = false;
-    if (parameters.parameters.isEmpty) {
-      argType = 'void';
-    } else {
-      final dart_ast.FormalParameter firstParameter =
-          parameters.parameters.first;
-      final dart_ast.TypeName typeName = firstParameter.childEntities
-          // ignore: always_specify_types
-          .firstWhere((e) => e is dart_ast.TypeName) as dart_ast.TypeName;
-      argType = typeName.name.name;
-      isNullable = typeName.question != null;
-    }
+    final List<Field> arguments =
+        parameters.parameters.map(formalParameterToField).toList();
     final bool isAsynchronous = _hasMetadata(node.metadata, 'async');
     if (_currentApi != null) {
       _currentApi!.methods.add(Method(
           name: node.name.name,
-          returnType: node.returnType.toString(),
-          argType: argType,
-          isReturnNullable: node.returnType!.question != null,
-          isArgNullable: isNullable,
+          returnType: Field(
+              name: '',
+              dataType: getFirstChildOfType<dart_ast.SimpleIdentifier>(
+                      node.returnType!)!
+                  .name,
+              typeArguments: typeAnnotationsToTypeArguments(
+                  (node.returnType as dart_ast.NamedType?)!.typeArguments),
+              isNullable: node.returnType!.question != null),
+          arguments: arguments,
           isAsynchronous: isAsynchronous,
           offset: node.offset));
     } else if (_currentClass != null) {
@@ -660,6 +695,23 @@ class _RootBuilder extends dart_ast_visitor.RecursiveAstVisitor<Object?> {
     return null;
   }
 
+  List<TypeArgument>? typeAnnotationsToTypeArguments(
+      dart_ast.TypeArgumentList? typeArguments) {
+    List<TypeArgument>? result;
+    if (typeArguments != null) {
+      for (final Object x in typeArguments.childEntities) {
+        if (x is dart_ast.TypeName) {
+          result ??= <TypeArgument>[];
+          result.add(TypeArgument(
+              dataType: x.name.name,
+              isNullable: x.question != null,
+              typeArguments: typeAnnotationsToTypeArguments(x.typeArguments)));
+        }
+      }
+    }
+    return result;
+  }
+
   @override
   Object? visitFieldDeclaration(dart_ast.FieldDeclaration node) {
     if (_currentClass != null) {
@@ -683,20 +735,7 @@ class _RootBuilder extends dart_ast_visitor.RecursiveAstVisitor<Object?> {
             name: node.fields.variables[0].name.name,
             dataType: type.name.name,
             isNullable: type.question != null,
-            // TODO(aaclarke): This probably has to be recursive at some point.
-            // ignore: prefer_null_aware_operators
-            typeArguments: typeArguments == null
-                ? null
-                : typeArguments.arguments
-                    .map((dart_ast.TypeAnnotation e) => Field(
-                          name: '',
-                          dataType: (e.childEntities.first
-                                  as dart_ast.SimpleIdentifier)
-                              .name,
-                          isNullable: e.question != null,
-                          offset: e.offset,
-                        ))
-                    .toList(),
+            typeArguments: typeAnnotationsToTypeArguments(typeArguments),
             offset: node.offset,
           ));
         }
@@ -764,7 +803,7 @@ class Pigeon {
         final ParsedUnitResult result =
             session.getParsedUnit2(path) as ParsedUnitResult;
         if (result.errors.isEmpty) {
-          final CompilationUnit unit = result.unit;
+          final dart_ast.CompilationUnit unit = result.unit;
           unit.accept(rootBuilder);
         } else {
           for (final AnalysisError error in result.errors) {
diff --git a/packages/pigeon/pigeons/all_datatypes.dart b/packages/pigeon/pigeons/all_datatypes.dart
index 0a8c2c27626f..138b4caf62c3 100644
--- a/packages/pigeon/pigeons/all_datatypes.dart
+++ b/packages/pigeon/pigeons/all_datatypes.dart
@@ -17,6 +17,8 @@ class Everything {
   List? aList;
   // ignore: always_specify_types
   Map? aMap;
+  List<List<bool?>?>? nestedList;
+  Map<String?, String?>? mapWithAnnotations;
 }
 
 @HostApi()
diff --git a/packages/pigeon/pigeons/primitive.dart b/packages/pigeon/pigeons/primitive.dart
index 2b453532b084..cc8eea5cc49c 100644
--- a/packages/pigeon/pigeons/primitive.dart
+++ b/packages/pigeon/pigeons/primitive.dart
@@ -15,6 +15,8 @@ abstract class PrimitiveHostApi {
   // ignore: always_specify_types
   List aList(List value);
   Int32List anInt32List(Int32List value);
+  List<bool?> aBoolList(List<bool?> value);
+  Map<String?, int?> aStringIntMap(Map<String?, int?> value);
 }
 
 @FlutterApi()
@@ -28,4 +30,6 @@ abstract class PrimitiveFlutterApi {
   // ignore: always_specify_types
   List aList(List value);
   Int32List anInt32List(Int32List value);
+  List<bool?> aBoolList(List<bool?> value);
+  Map<String?, int?> aStringIntMap(Map<String?, int?> value);
 }
diff --git a/packages/pigeon/platform_tests/android_unit_tests/android/app/src/test/java/com/example/android_unit_tests/PrimitiveTest.java b/packages/pigeon/platform_tests/android_unit_tests/android/app/src/test/java/com/example/android_unit_tests/PrimitiveTest.java
index 36ce51cd35a0..d557d2154049 100644
--- a/packages/pigeon/platform_tests/android_unit_tests/android/app/src/test/java/com/example/android_unit_tests/PrimitiveTest.java
+++ b/packages/pigeon/platform_tests/android_unit_tests/android/app/src/test/java/com/example/android_unit_tests/PrimitiveTest.java
@@ -37,10 +37,10 @@ public void primitiveInt() {
     PrimitiveFlutterApi api = new PrimitiveFlutterApi(binaryMessenger);
     boolean[] didCall = {false};
     api.anInt(
-        1,
-        (Integer result) -> {
+        1L,
+        (Long result) -> {
           didCall[0] = true;
-          assertEquals(result, (Integer) 1);
+          assertEquals(result, (Long) 1L);
         });
     assertTrue(didCall[0]);
   }
@@ -94,7 +94,7 @@ public void primitiveMap() {
     boolean[] didCall = {false};
     api.aMap(
         Collections.singletonMap("hello", 1),
-        (Map result) -> {
+        (Map<Object, Object> result) -> {
           didCall[0] = true;
           assertEquals(result, Collections.singletonMap("hello", 1));
         });
@@ -108,7 +108,7 @@ public void primitiveList() {
     boolean[] didCall = {false};
     api.aList(
         Collections.singletonList("hello"),
-        (List result) -> {
+        (List<Object> result) -> {
           didCall[0] = true;
           assertEquals(result, Collections.singletonList("hello"));
         });
diff --git a/packages/pigeon/platform_tests/flutter_null_safe_unit_tests/lib/all_datatypes.dart b/packages/pigeon/platform_tests/flutter_null_safe_unit_tests/lib/all_datatypes.dart
index 09db4570911d..adf2c866aa95 100644
--- a/packages/pigeon/platform_tests/flutter_null_safe_unit_tests/lib/all_datatypes.dart
+++ b/packages/pigeon/platform_tests/flutter_null_safe_unit_tests/lib/all_datatypes.dart
@@ -23,6 +23,8 @@ class Everything {
   Float64List? aFloatArray;
   List<Object?>? aList;
   Map<Object?, Object?>? aMap;
+  List<List<bool?>?>? nestedList;
+  Map<String?, String?>? mapWithAnnotations;
 
   Object encode() {
     final Map<Object?, Object?> pigeonMap = <Object?, Object?>{};
@@ -36,6 +38,8 @@ class Everything {
     pigeonMap['aFloatArray'] = aFloatArray;
     pigeonMap['aList'] = aList;
     pigeonMap['aMap'] = aMap;
+    pigeonMap['nestedList'] = nestedList;
+    pigeonMap['mapWithAnnotations'] = mapWithAnnotations;
     return pigeonMap;
   }
 
@@ -51,7 +55,12 @@ class Everything {
       ..a8ByteArray = pigeonMap['a8ByteArray'] as Int64List?
       ..aFloatArray = pigeonMap['aFloatArray'] as Float64List?
       ..aList = pigeonMap['aList'] as List<Object?>?
-      ..aMap = pigeonMap['aMap'] as Map<Object?, Object?>?;
+      ..aMap = pigeonMap['aMap'] as Map<Object?, Object?>?
+      ..nestedList =
+          (pigeonMap['nestedList'] as List<Object?>?)?.cast<List<bool?>?>()
+      ..mapWithAnnotations =
+          (pigeonMap['mapWithAnnotations'] as Map<Object?, Object?>?)
+              ?.cast<String?, String?>();
   }
 }
 
diff --git a/packages/pigeon/platform_tests/flutter_null_safe_unit_tests/lib/primitive.dart b/packages/pigeon/platform_tests/flutter_null_safe_unit_tests/lib/primitive.dart
new file mode 100644
index 000000000000..ae36e10b22c4
--- /dev/null
+++ b/packages/pigeon/platform_tests/flutter_null_safe_unit_tests/lib/primitive.dart
@@ -0,0 +1,411 @@
+// Copyright 2013 The Flutter Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+//
+// Autogenerated from Pigeon (v0.3.0), do not edit directly.
+// See also: https://pub.dev/packages/pigeon
+// ignore_for_file: public_member_api_docs, non_constant_identifier_names, avoid_as, unused_import, unnecessary_parenthesis, prefer_null_aware_operators, omit_local_variable_types, unused_shown_name
+// @dart = 2.12
+import 'dart:async';
+import 'dart:typed_data' show Uint8List, Int32List, Int64List, Float64List;
+
+import 'package:flutter/foundation.dart' show WriteBuffer, ReadBuffer;
+import 'package:flutter/services.dart';
+
+class _PrimitiveHostApiCodec extends StandardMessageCodec {
+  const _PrimitiveHostApiCodec();
+}
+
+class PrimitiveHostApi {
+  /// Constructor for [PrimitiveHostApi].  The [binaryMessenger] named argument is
+  /// available for dependency injection.  If it is left null, the default
+  /// BinaryMessenger will be used which routes to the host platform.
+  PrimitiveHostApi({BinaryMessenger? binaryMessenger})
+      : _binaryMessenger = binaryMessenger;
+
+  final BinaryMessenger? _binaryMessenger;
+
+  static const MessageCodec<Object?> codec = _PrimitiveHostApiCodec();
+
+  Future<int> anInt(int arg) async {
+    final BasicMessageChannel<Object?> channel = BasicMessageChannel<Object?>(
+        'dev.flutter.pigeon.PrimitiveHostApi.anInt', codec,
+        binaryMessenger: _binaryMessenger);
+    final Map<Object?, Object?>? replyMap =
+        await channel.send(arg) as Map<Object?, Object?>?;
+    if (replyMap == null) {
+      throw PlatformException(
+        code: 'channel-error',
+        message: 'Unable to establish connection on channel.',
+        details: null,
+      );
+    } else if (replyMap['error'] != null) {
+      final Map<Object?, Object?> error =
+          (replyMap['error'] as Map<Object?, Object?>?)!;
+      throw PlatformException(
+        code: (error['code'] as String?)!,
+        message: error['message'] as String?,
+        details: error['details'],
+      );
+    } else {
+      return (replyMap['result'] as int?)!;
+    }
+  }
+
+  Future<bool> aBool(bool arg) async {
+    final BasicMessageChannel<Object?> channel = BasicMessageChannel<Object?>(
+        'dev.flutter.pigeon.PrimitiveHostApi.aBool', codec,
+        binaryMessenger: _binaryMessenger);
+    final Map<Object?, Object?>? replyMap =
+        await channel.send(arg) as Map<Object?, Object?>?;
+    if (replyMap == null) {
+      throw PlatformException(
+        code: 'channel-error',
+        message: 'Unable to establish connection on channel.',
+        details: null,
+      );
+    } else if (replyMap['error'] != null) {
+      final Map<Object?, Object?> error =
+          (replyMap['error'] as Map<Object?, Object?>?)!;
+      throw PlatformException(
+        code: (error['code'] as String?)!,
+        message: error['message'] as String?,
+        details: error['details'],
+      );
+    } else {
+      return (replyMap['result'] as bool?)!;
+    }
+  }
+
+  Future<String> aString(String arg) async {
+    final BasicMessageChannel<Object?> channel = BasicMessageChannel<Object?>(
+        'dev.flutter.pigeon.PrimitiveHostApi.aString', codec,
+        binaryMessenger: _binaryMessenger);
+    final Map<Object?, Object?>? replyMap =
+        await channel.send(arg) as Map<Object?, Object?>?;
+    if (replyMap == null) {
+      throw PlatformException(
+        code: 'channel-error',
+        message: 'Unable to establish connection on channel.',
+        details: null,
+      );
+    } else if (replyMap['error'] != null) {
+      final Map<Object?, Object?> error =
+          (replyMap['error'] as Map<Object?, Object?>?)!;
+      throw PlatformException(
+        code: (error['code'] as String?)!,
+        message: error['message'] as String?,
+        details: error['details'],
+      );
+    } else {
+      return (replyMap['result'] as String?)!;
+    }
+  }
+
+  Future<double> aDouble(double arg) async {
+    final BasicMessageChannel<Object?> channel = BasicMessageChannel<Object?>(
+        'dev.flutter.pigeon.PrimitiveHostApi.aDouble', codec,
+        binaryMessenger: _binaryMessenger);
+    final Map<Object?, Object?>? replyMap =
+        await channel.send(arg) as Map<Object?, Object?>?;
+    if (replyMap == null) {
+      throw PlatformException(
+        code: 'channel-error',
+        message: 'Unable to establish connection on channel.',
+        details: null,
+      );
+    } else if (replyMap['error'] != null) {
+      final Map<Object?, Object?> error =
+          (replyMap['error'] as Map<Object?, Object?>?)!;
+      throw PlatformException(
+        code: (error['code'] as String?)!,
+        message: error['message'] as String?,
+        details: error['details'],
+      );
+    } else {
+      return (replyMap['result'] as double?)!;
+    }
+  }
+
+  Future<Map<Object?, Object?>> aMap(Map<Object?, Object?> arg) async {
+    final BasicMessageChannel<Object?> channel = BasicMessageChannel<Object?>(
+        'dev.flutter.pigeon.PrimitiveHostApi.aMap', codec,
+        binaryMessenger: _binaryMessenger);
+    final Map<Object?, Object?>? replyMap =
+        await channel.send(arg) as Map<Object?, Object?>?;
+    if (replyMap == null) {
+      throw PlatformException(
+        code: 'channel-error',
+        message: 'Unable to establish connection on channel.',
+        details: null,
+      );
+    } else if (replyMap['error'] != null) {
+      final Map<Object?, Object?> error =
+          (replyMap['error'] as Map<Object?, Object?>?)!;
+      throw PlatformException(
+        code: (error['code'] as String?)!,
+        message: error['message'] as String?,
+        details: error['details'],
+      );
+    } else {
+      return (replyMap['result'] as Map<Object?, Object?>?)!;
+    }
+  }
+
+  Future<List<Object?>> aList(List<Object?> arg) async {
+    final BasicMessageChannel<Object?> channel = BasicMessageChannel<Object?>(
+        'dev.flutter.pigeon.PrimitiveHostApi.aList', codec,
+        binaryMessenger: _binaryMessenger);
+    final Map<Object?, Object?>? replyMap =
+        await channel.send(arg) as Map<Object?, Object?>?;
+    if (replyMap == null) {
+      throw PlatformException(
+        code: 'channel-error',
+        message: 'Unable to establish connection on channel.',
+        details: null,
+      );
+    } else if (replyMap['error'] != null) {
+      final Map<Object?, Object?> error =
+          (replyMap['error'] as Map<Object?, Object?>?)!;
+      throw PlatformException(
+        code: (error['code'] as String?)!,
+        message: error['message'] as String?,
+        details: error['details'],
+      );
+    } else {
+      return (replyMap['result'] as List<Object?>?)!;
+    }
+  }
+
+  Future<Int32List> anInt32List(Int32List arg) async {
+    final BasicMessageChannel<Object?> channel = BasicMessageChannel<Object?>(
+        'dev.flutter.pigeon.PrimitiveHostApi.anInt32List', codec,
+        binaryMessenger: _binaryMessenger);
+    final Map<Object?, Object?>? replyMap =
+        await channel.send(arg) as Map<Object?, Object?>?;
+    if (replyMap == null) {
+      throw PlatformException(
+        code: 'channel-error',
+        message: 'Unable to establish connection on channel.',
+        details: null,
+      );
+    } else if (replyMap['error'] != null) {
+      final Map<Object?, Object?> error =
+          (replyMap['error'] as Map<Object?, Object?>?)!;
+      throw PlatformException(
+        code: (error['code'] as String?)!,
+        message: error['message'] as String?,
+        details: error['details'],
+      );
+    } else {
+      return (replyMap['result'] as Int32List?)!;
+    }
+  }
+
+  Future<List<bool?>> aBoolList(List<bool?> arg) async {
+    final BasicMessageChannel<Object?> channel = BasicMessageChannel<Object?>(
+        'dev.flutter.pigeon.PrimitiveHostApi.aBoolList', codec,
+        binaryMessenger: _binaryMessenger);
+    final Map<Object?, Object?>? replyMap =
+        await channel.send(arg) as Map<Object?, Object?>?;
+    if (replyMap == null) {
+      throw PlatformException(
+        code: 'channel-error',
+        message: 'Unable to establish connection on channel.',
+        details: null,
+      );
+    } else if (replyMap['error'] != null) {
+      final Map<Object?, Object?> error =
+          (replyMap['error'] as Map<Object?, Object?>?)!;
+      throw PlatformException(
+        code: (error['code'] as String?)!,
+        message: error['message'] as String?,
+        details: error['details'],
+      );
+    } else {
+      return (replyMap['result'] as List<Object?>?)!.cast<bool?>();
+    }
+  }
+
+  Future<Map<String?, int?>> aStringIntMap(Map<String?, int?> arg) async {
+    final BasicMessageChannel<Object?> channel = BasicMessageChannel<Object?>(
+        'dev.flutter.pigeon.PrimitiveHostApi.aStringIntMap', codec,
+        binaryMessenger: _binaryMessenger);
+    final Map<Object?, Object?>? replyMap =
+        await channel.send(arg) as Map<Object?, Object?>?;
+    if (replyMap == null) {
+      throw PlatformException(
+        code: 'channel-error',
+        message: 'Unable to establish connection on channel.',
+        details: null,
+      );
+    } else if (replyMap['error'] != null) {
+      final Map<Object?, Object?> error =
+          (replyMap['error'] as Map<Object?, Object?>?)!;
+      throw PlatformException(
+        code: (error['code'] as String?)!,
+        message: error['message'] as String?,
+        details: error['details'],
+      );
+    } else {
+      return (replyMap['result'] as Map<Object?, Object?>?)!
+          .cast<String?, int?>();
+    }
+  }
+}
+
+class _PrimitiveFlutterApiCodec extends StandardMessageCodec {
+  const _PrimitiveFlutterApiCodec();
+}
+
+abstract class PrimitiveFlutterApi {
+  static const MessageCodec<Object?> codec = _PrimitiveFlutterApiCodec();
+
+  int anInt(int arg);
+  bool aBool(bool arg);
+  String aString(String arg);
+  double aDouble(double arg);
+  Map<Object?, Object?> aMap(Map<Object?, Object?> arg);
+  List<Object?> aList(List<Object?> arg);
+  Int32List anInt32List(Int32List arg);
+  List<bool?> aBoolList(List<bool?> arg);
+  Map<String?, int?> aStringIntMap(Map<String?, int?> arg);
+  static void setup(PrimitiveFlutterApi? api) {
+    {
+      const BasicMessageChannel<Object?> channel = BasicMessageChannel<Object?>(
+          'dev.flutter.pigeon.PrimitiveFlutterApi.anInt', codec);
+      if (api == null) {
+        channel.setMessageHandler(null);
+      } else {
+        channel.setMessageHandler((Object? message) async {
+          assert(message != null,
+              'Argument for dev.flutter.pigeon.PrimitiveFlutterApi.anInt was null. Expected int.');
+          final int input = (message as int?)!;
+          final int output = api.anInt(input);
+          return output;
+        });
+      }
+    }
+    {
+      const BasicMessageChannel<Object?> channel = BasicMessageChannel<Object?>(
+          'dev.flutter.pigeon.PrimitiveFlutterApi.aBool', codec);
+      if (api == null) {
+        channel.setMessageHandler(null);
+      } else {
+        channel.setMessageHandler((Object? message) async {
+          assert(message != null,
+              'Argument for dev.flutter.pigeon.PrimitiveFlutterApi.aBool was null. Expected bool.');
+          final bool input = (message as bool?)!;
+          final bool output = api.aBool(input);
+          return output;
+        });
+      }
+    }
+    {
+      const BasicMessageChannel<Object?> channel = BasicMessageChannel<Object?>(
+          'dev.flutter.pigeon.PrimitiveFlutterApi.aString', codec);
+      if (api == null) {
+        channel.setMessageHandler(null);
+      } else {
+        channel.setMessageHandler((Object? message) async {
+          assert(message != null,
+              'Argument for dev.flutter.pigeon.PrimitiveFlutterApi.aString was null. Expected String.');
+          final String input = (message as String?)!;
+          final String output = api.aString(input);
+          return output;
+        });
+      }
+    }
+    {
+      const BasicMessageChannel<Object?> channel = BasicMessageChannel<Object?>(
+          'dev.flutter.pigeon.PrimitiveFlutterApi.aDouble', codec);
+      if (api == null) {
+        channel.setMessageHandler(null);
+      } else {
+        channel.setMessageHandler((Object? message) async {
+          assert(message != null,
+              'Argument for dev.flutter.pigeon.PrimitiveFlutterApi.aDouble was null. Expected double.');
+          final double input = (message as double?)!;
+          final double output = api.aDouble(input);
+          return output;
+        });
+      }
+    }
+    {
+      const BasicMessageChannel<Object?> channel = BasicMessageChannel<Object?>(
+          'dev.flutter.pigeon.PrimitiveFlutterApi.aMap', codec);
+      if (api == null) {
+        channel.setMessageHandler(null);
+      } else {
+        channel.setMessageHandler((Object? message) async {
+          assert(message != null,
+              'Argument for dev.flutter.pigeon.PrimitiveFlutterApi.aMap was null. Expected Map<Object?, Object?>.');
+          final Map<Object?, Object?> input =
+              (message as Map<Object?, Object?>?)!;
+          final Map<Object?, Object?> output = api.aMap(input);
+          return output;
+        });
+      }
+    }
+    {
+      const BasicMessageChannel<Object?> channel = BasicMessageChannel<Object?>(
+          'dev.flutter.pigeon.PrimitiveFlutterApi.aList', codec);
+      if (api == null) {
+        channel.setMessageHandler(null);
+      } else {
+        channel.setMessageHandler((Object? message) async {
+          assert(message != null,
+              'Argument for dev.flutter.pigeon.PrimitiveFlutterApi.aList was null. Expected List<Object?>.');
+          final List<Object?> input = (message as List<Object?>?)!;
+          final List<Object?> output = api.aList(input);
+          return output;
+        });
+      }
+    }
+    {
+      const BasicMessageChannel<Object?> channel = BasicMessageChannel<Object?>(
+          'dev.flutter.pigeon.PrimitiveFlutterApi.anInt32List', codec);
+      if (api == null) {
+        channel.setMessageHandler(null);
+      } else {
+        channel.setMessageHandler((Object? message) async {
+          assert(message != null,
+              'Argument for dev.flutter.pigeon.PrimitiveFlutterApi.anInt32List was null. Expected Int32List.');
+          final Int32List input = (message as Int32List?)!;
+          final Int32List output = api.anInt32List(input);
+          return output;
+        });
+      }
+    }
+    {
+      const BasicMessageChannel<Object?> channel = BasicMessageChannel<Object?>(
+          'dev.flutter.pigeon.PrimitiveFlutterApi.aBoolList', codec);
+      if (api == null) {
+        channel.setMessageHandler(null);
+      } else {
+        channel.setMessageHandler((Object? message) async {
+          assert(message != null,
+              'Argument for dev.flutter.pigeon.PrimitiveFlutterApi.aBoolList was null. Expected List<bool?>.');
+          final List<bool?> input = (message as List<bool?>?)!;
+          final List<bool?> output = api.aBoolList(input);
+          return output;
+        });
+      }
+    }
+    {
+      const BasicMessageChannel<Object?> channel = BasicMessageChannel<Object?>(
+          'dev.flutter.pigeon.PrimitiveFlutterApi.aStringIntMap', codec);
+      if (api == null) {
+        channel.setMessageHandler(null);
+      } else {
+        channel.setMessageHandler((Object? message) async {
+          assert(message != null,
+              'Argument for dev.flutter.pigeon.PrimitiveFlutterApi.aStringIntMap was null. Expected Map<String?, int?>.');
+          final Map<String?, int?> input = (message as Map<String?, int?>?)!;
+          final Map<String?, int?> output = api.aStringIntMap(input);
+          return output;
+        });
+      }
+    }
+  }
+}
diff --git a/packages/pigeon/platform_tests/flutter_null_safe_unit_tests/test/all_datatypes_test.dart b/packages/pigeon/platform_tests/flutter_null_safe_unit_tests/test/all_datatypes_test.dart
index 7061fb8fa47a..4cad76d88853 100644
--- a/packages/pigeon/platform_tests/flutter_null_safe_unit_tests/test/all_datatypes_test.dart
+++ b/packages/pigeon/platform_tests/flutter_null_safe_unit_tests/test/all_datatypes_test.dart
@@ -35,6 +35,8 @@ void main() {
     expect(result.aFloatArray, isNull);
     expect(result.aList, isNull);
     expect(result.aMap, isNull);
+    expect(result.nestedList, isNull);
+    expect(result.mapWithAnnotations, isNull);
   });
 
   test('with values', () async {
@@ -50,6 +52,10 @@ void main() {
         Float64List.fromList(<double>[1.0, 2.5, 3.0, 4.25]);
     everything.aList = <int>[1, 2, 3, 4];
     everything.aMap = <String, int>{'hello': 1234};
+    everything.aList = <List<bool?>>[
+      <bool?>[true]
+    ];
+    everything.mapWithAnnotations = <String?, String?>{'hello': 'world'};
     final BinaryMessenger mockMessenger = MockBinaryMessenger();
     when(mockMessenger.send('dev.flutter.pigeon.HostEverything.echo', any))
         .thenAnswer((Invocation realInvocation) async {
@@ -70,5 +76,7 @@ void main() {
     expect(result.aFloatArray, everything.aFloatArray);
     expect(result.aList, everything.aList);
     expect(result.aMap, everything.aMap);
+    expect(result.aList, everything.aList);
+    expect(result.mapWithAnnotations, everything.mapWithAnnotations);
   });
 }
diff --git a/packages/pigeon/platform_tests/flutter_null_safe_unit_tests/test/primitive_test.dart b/packages/pigeon/platform_tests/flutter_null_safe_unit_tests/test/primitive_test.dart
new file mode 100644
index 000000000000..3c20172496a9
--- /dev/null
+++ b/packages/pigeon/platform_tests/flutter_null_safe_unit_tests/test/primitive_test.dart
@@ -0,0 +1,61 @@
+// Copyright 2013 The Flutter Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+import 'package:flutter/services.dart';
+import 'package:flutter_test/flutter_test.dart';
+import 'package:flutter_unit_tests/primitive.dart';
+import 'package:mockito/annotations.dart';
+import 'package:mockito/mockito.dart';
+import 'primitive_test.mocks.dart';
+
+@GenerateMocks(<Type>[BinaryMessenger])
+void main() {
+  test('test anInt', () async {
+    final BinaryMessenger mockMessenger = MockBinaryMessenger();
+    when(mockMessenger.send('dev.flutter.pigeon.PrimitiveHostApi.anInt', any))
+        .thenAnswer((Invocation realInvocation) async {
+      const MessageCodec<Object?> codec = PrimitiveHostApi.codec;
+      final Object? input =
+          codec.decodeMessage(realInvocation.positionalArguments[1]);
+      return codec.encodeMessage(<String, Object>{'result': input!});
+    });
+    final PrimitiveHostApi api =
+        PrimitiveHostApi(binaryMessenger: mockMessenger);
+    final int result = await api.anInt(1);
+    expect(result, 1);
+  });
+
+  test('test List<bool>', () async {
+    final BinaryMessenger mockMessenger = MockBinaryMessenger();
+    when(mockMessenger.send(
+            'dev.flutter.pigeon.PrimitiveHostApi.aBoolList', any))
+        .thenAnswer((Invocation realInvocation) async {
+      const MessageCodec<Object?> codec = PrimitiveHostApi.codec;
+      final Object? input =
+          codec.decodeMessage(realInvocation.positionalArguments[1]);
+      return codec.encodeMessage(<String, Object>{'result': input!});
+    });
+    final PrimitiveHostApi api =
+        PrimitiveHostApi(binaryMessenger: mockMessenger);
+    final List<bool?> result = await api.aBoolList(<bool?>[true]);
+    expect(result[0], true);
+  });
+
+  test('test Map<String?, int?>', () async {
+    final BinaryMessenger mockMessenger = MockBinaryMessenger();
+    when(mockMessenger.send(
+            'dev.flutter.pigeon.PrimitiveHostApi.aStringIntMap', any))
+        .thenAnswer((Invocation realInvocation) async {
+      const MessageCodec<Object?> codec = PrimitiveHostApi.codec;
+      final Object? input =
+          codec.decodeMessage(realInvocation.positionalArguments[1]);
+      return codec.encodeMessage(<String, Object>{'result': input!});
+    });
+    final PrimitiveHostApi api =
+        PrimitiveHostApi(binaryMessenger: mockMessenger);
+    final Map<String?, int?> result =
+        await api.aStringIntMap(<String?, int?>{'hello': 1});
+    expect(result['hello'], 1);
+  });
+}
diff --git a/packages/pigeon/platform_tests/flutter_null_safe_unit_tests/test/primitive_test.mocks.dart b/packages/pigeon/platform_tests/flutter_null_safe_unit_tests/test/primitive_test.mocks.dart
new file mode 100644
index 000000000000..814ea419359e
--- /dev/null
+++ b/packages/pigeon/platform_tests/flutter_null_safe_unit_tests/test/primitive_test.mocks.dart
@@ -0,0 +1,44 @@
+// Mocks generated by Mockito 5.0.7 from annotations
+// in flutter_unit_tests/test/null_safe_test.dart.
+// Do not manually edit this file.
+
+import 'dart:async' as _i3;
+import 'dart:typed_data' as _i4;
+import 'dart:ui' as _i5;
+
+import 'package:flutter/src/services/binary_messenger.dart' as _i2;
+import 'package:mockito/mockito.dart' as _i1;
+
+// ignore_for_file: comment_references
+// ignore_for_file: unnecessary_parenthesis
+// ignore_for_file: always_specify_types
+// Added manually; several methods have moved to
+// flutter_test/lib/src/deprecated.dart on master, but that hasn't reached
+// stable yet.
+// ignore_for_file: override_on_non_overriding_member
+
+/// A class which mocks [BinaryMessenger].
+///
+/// See the documentation for Mockito's code generation for more information.
+class MockBinaryMessenger extends _i1.Mock implements _i2.BinaryMessenger {
+  MockBinaryMessenger() {
+    _i1.throwOnMissingStub(this);
+  }
+
+  @override
+  _i3.Future<void> handlePlatformMessage(String? channel, _i4.ByteData? data,
+          _i5.PlatformMessageResponseCallback? callback) =>
+      (super.noSuchMethod(
+          Invocation.method(#handlePlatformMessage, [channel, data, callback]),
+          returnValue: Future<void>.value(null),
+          returnValueForMissingStub:
+              Future<dynamic>.value()) as _i3.Future<void>);
+  @override
+  _i3.Future<_i4.ByteData?>? send(String? channel, _i4.ByteData? message) =>
+      (super.noSuchMethod(Invocation.method(#send, [channel, message]))
+          as _i3.Future<_i4.ByteData?>?);
+  @override
+  void setMessageHandler(String? channel, _i2.MessageHandler? handler) => super
+      .noSuchMethod(Invocation.method(#setMessageHandler, [channel, handler]),
+          returnValueForMissingStub: null);
+}
diff --git a/packages/pigeon/run_tests.sh b/packages/pigeon/run_tests.sh
index 341967574189..2ed2c295b38f 100755
--- a/packages/pigeon/run_tests.sh
+++ b/packages/pigeon/run_tests.sh
@@ -194,17 +194,22 @@ test_running_without_arguments() {
 }
 
 run_flutter_unittests() {
+  local flutter_tests="platform_tests/flutter_null_safe_unit_tests"
   pushd $PWD
   $run_pigeon \
     --input pigeons/flutter_unittests.dart \
-    --dart_out platform_tests/flutter_null_safe_unit_tests/lib/null_safe_pigeon.dart
+    --dart_out "$flutter_tests/lib/null_safe_pigeon.dart"
   $run_pigeon \
     --input pigeons/all_datatypes.dart \
-    --dart_out platform_tests/flutter_null_safe_unit_tests/lib/all_datatypes.dart
-  cd platform_tests/flutter_null_safe_unit_tests
+    --dart_out "$flutter_tests/lib/all_datatypes.dart"
+  $run_pigeon \
+    --input pigeons/primitive.dart \
+    --dart_out "$flutter_tests/lib/primitive.dart"
+  cd "$flutter_tests"
   flutter pub get
   flutter test test/null_safe_test.dart
   flutter test test/all_datatypes_test.dart
+  flutter test test/primitive_test.dart
   popd
 }
 
diff --git a/packages/pigeon/test/dart_generator_test.dart b/packages/pigeon/test/dart_generator_test.dart
index 04b3488b303d..225704e073f2 100644
--- a/packages/pigeon/test/dart_generator_test.dart
+++ b/packages/pigeon/test/dart_generator_test.dart
@@ -57,9 +57,10 @@ void main() {
       Api(name: 'Api', location: ApiLocation.host, methods: <Method>[
         Method(
           name: 'doSomething',
-          argType: 'Input',
-          isArgNullable: false,
-          returnType: 'Output',
+          arguments: <Field>[
+            Field(name: '', isNullable: false, dataType: 'Input')
+          ],
+          returnType: Field(name: '', dataType: 'Output', isNullable: false),
           isAsynchronous: false,
         )
       ])
@@ -131,9 +132,10 @@ void main() {
       Api(name: 'Api', location: ApiLocation.flutter, methods: <Method>[
         Method(
           name: 'doSomething',
-          argType: 'Input',
-          isArgNullable: false,
-          returnType: 'Output',
+          arguments: <Field>[
+            Field(name: '', isNullable: false, dataType: 'Input')
+          ],
+          returnType: Field(name: '', dataType: 'Output', isNullable: false),
           isAsynchronous: false,
         )
       ])
@@ -165,9 +167,10 @@ void main() {
       Api(name: 'Api', location: ApiLocation.host, methods: <Method>[
         Method(
           name: 'doSomething',
-          argType: 'Input',
-          isArgNullable: false,
-          returnType: 'void',
+          arguments: <Field>[
+            Field(name: '', isNullable: false, dataType: 'Input')
+          ],
+          returnType: Field(name: '', dataType: 'void', isNullable: false),
           isAsynchronous: false,
         )
       ])
@@ -192,9 +195,10 @@ void main() {
       Api(name: 'Api', location: ApiLocation.flutter, methods: <Method>[
         Method(
           name: 'doSomething',
-          argType: 'Input',
-          isArgNullable: false,
-          returnType: 'void',
+          arguments: <Field>[
+            Field(name: '', isNullable: false, dataType: 'Input')
+          ],
+          returnType: Field(name: '', dataType: 'void', isNullable: false),
           isAsynchronous: false,
         )
       ])
@@ -222,9 +226,8 @@ void main() {
       Api(name: 'Api', location: ApiLocation.flutter, methods: <Method>[
         Method(
           name: 'doSomething',
-          argType: 'void',
-          isArgNullable: false,
-          returnType: 'Output',
+          arguments: <Field>[],
+          returnType: Field(name: '', dataType: 'Output', isNullable: false),
           isAsynchronous: false,
         )
       ])
@@ -249,9 +252,10 @@ void main() {
       Api(name: 'Api', location: ApiLocation.flutter, methods: <Method>[
         Method(
           name: 'doSomething',
-          argType: 'EnumClass',
-          isArgNullable: false,
-          returnType: 'EnumClass',
+          arguments: <Field>[
+            Field(name: '', isNullable: false, dataType: 'EnumClass')
+          ],
+          returnType: Field(name: '', dataType: 'EnumClass', isNullable: false),
           isAsynchronous: false,
         )
       ])
@@ -286,9 +290,10 @@ void main() {
       Api(name: 'Api', location: ApiLocation.flutter, methods: <Method>[
         Method(
           name: 'doSomething',
-          argType: 'EnumClass',
-          isArgNullable: false,
-          returnType: 'EnumClass',
+          arguments: <Field>[
+            Field(name: '', isNullable: false, dataType: 'EnumClass')
+          ],
+          returnType: Field(name: '', dataType: 'EnumClass', isNullable: false),
           isAsynchronous: false,
         )
       ])
@@ -325,9 +330,8 @@ void main() {
       Api(name: 'Api', location: ApiLocation.host, methods: <Method>[
         Method(
           name: 'doSomething',
-          argType: 'void',
-          isArgNullable: false,
-          returnType: 'Output',
+          arguments: <Field>[],
+          returnType: Field(name: '', dataType: 'Output', isNullable: false),
           isAsynchronous: false,
         )
       ])
@@ -355,16 +359,19 @@ void main() {
           methods: <Method>[
             Method(
               name: 'doSomething',
-              argType: 'Input',
-              isArgNullable: false,
-              returnType: 'Output',
+              arguments: <Field>[
+                Field(name: '', isNullable: false, dataType: 'Input')
+              ],
+              returnType:
+                  Field(name: '', dataType: 'Output', isNullable: false),
               isAsynchronous: false,
             ),
             Method(
               name: 'voidReturner',
-              argType: 'Input',
-              isArgNullable: false,
-              returnType: 'void',
+              arguments: <Field>[
+                Field(name: '', isNullable: false, dataType: 'Input')
+              ],
+              returnType: Field(name: '', dataType: 'void', isNullable: false),
               isAsynchronous: false,
             )
           ])
@@ -432,9 +439,10 @@ void main() {
       Api(name: 'Api', location: ApiLocation.flutter, methods: <Method>[
         Method(
           name: 'doSomething',
-          argType: 'Input',
-          isArgNullable: false,
-          returnType: 'Output',
+          arguments: <Field>[
+            Field(name: '', isNullable: false, dataType: 'Input')
+          ],
+          returnType: Field(name: '', dataType: 'Output', isNullable: false),
           isAsynchronous: true,
         )
       ])
@@ -468,9 +476,10 @@ void main() {
       Api(name: 'Api', location: ApiLocation.flutter, methods: <Method>[
         Method(
           name: 'doSomething',
-          argType: 'Input',
-          isArgNullable: false,
-          returnType: 'void',
+          arguments: <Field>[
+            Field(name: '', isNullable: false, dataType: 'Input')
+          ],
+          returnType: Field(name: '', dataType: 'void', isNullable: false),
           isAsynchronous: true,
         )
       ])
@@ -503,9 +512,10 @@ void main() {
       Api(name: 'Api', location: ApiLocation.host, methods: <Method>[
         Method(
           name: 'doSomething',
-          argType: 'Input',
-          isArgNullable: false,
-          returnType: 'Output',
+          arguments: <Field>[
+            Field(name: '', isNullable: false, dataType: 'Input')
+          ],
+          returnType: Field(name: '', dataType: 'Output', isNullable: false),
           isAsynchronous: true,
         )
       ])
@@ -537,9 +547,8 @@ void main() {
       Api(name: 'Api', location: ApiLocation.host, methods: <Method>[
         Method(
           name: 'doSomething',
-          argType: 'void',
-          isArgNullable: false,
-          returnType: 'Output',
+          arguments: <Field>[],
+          returnType: Field(name: '', dataType: 'Output', isNullable: false),
           isAsynchronous: true,
         )
       ])
@@ -574,4 +583,176 @@ void main() {
     final String code = sink.toString();
     expect(code, startsWith('// hello world'));
   });
+
+  test('generics', () {
+    final Class klass = Class(
+      name: 'Foobar',
+      fields: <Field>[
+        Field(
+          name: 'field1',
+          dataType: 'List',
+          isNullable: true,
+          typeArguments: <TypeArgument>[
+            TypeArgument(dataType: 'int', isNullable: true)
+          ],
+        ),
+      ],
+    );
+    final Root root = Root(
+      apis: <Api>[],
+      classes: <Class>[klass],
+      enums: <Enum>[],
+    );
+    final StringBuffer sink = StringBuffer();
+    generateDart(const DartOptions(isNullSafe: true), root, sink);
+    final String code = sink.toString();
+    expect(code, contains('class Foobar'));
+    expect(code, contains('  List<int?>? field1;'));
+  });
+
+  test('map generics', () {
+    final Class klass = Class(
+      name: 'Foobar',
+      fields: <Field>[
+        Field(
+          name: 'field1',
+          dataType: 'Map',
+          isNullable: true,
+          typeArguments: <TypeArgument>[
+            TypeArgument(dataType: 'String', isNullable: true),
+            TypeArgument(dataType: 'int', isNullable: true),
+          ],
+        ),
+      ],
+    );
+    final Root root = Root(
+      apis: <Api>[],
+      classes: <Class>[klass],
+      enums: <Enum>[],
+    );
+    final StringBuffer sink = StringBuffer();
+    generateDart(const DartOptions(isNullSafe: true), root, sink);
+    final String code = sink.toString();
+    expect(code, contains('class Foobar'));
+    expect(code, contains('  Map<String?, int?>? field1;'));
+  });
+
+  test('host generics argument', () {
+    final Root root = Root(
+      apis: <Api>[
+        Api(name: 'Api', location: ApiLocation.host, methods: <Method>[
+          Method(
+              name: 'doit',
+              returnType: Field(dataType: 'void', isNullable: false, name: ''),
+              arguments: <Field>[
+                Field(
+                    name: 'arg',
+                    dataType: 'List',
+                    isNullable: false,
+                    typeArguments: <TypeArgument>[
+                      TypeArgument(dataType: 'int', isNullable: true)
+                    ])
+              ])
+        ])
+      ],
+      classes: <Class>[],
+      enums: <Enum>[],
+    );
+    final StringBuffer sink = StringBuffer();
+    generateDart(const DartOptions(isNullSafe: true), root, sink);
+    final String code = sink.toString();
+    expect(code, contains('doit(List<int?> arg'));
+  });
+
+  test('flutter generics argument', () {
+    final Root root = Root(
+      apis: <Api>[
+        Api(name: 'Api', location: ApiLocation.flutter, methods: <Method>[
+          Method(
+              name: 'doit',
+              returnType: Field(dataType: 'void', isNullable: false, name: ''),
+              arguments: <Field>[
+                Field(
+                    name: 'arg',
+                    dataType: 'List',
+                    isNullable: false,
+                    typeArguments: <TypeArgument>[
+                      TypeArgument(dataType: 'int', isNullable: true)
+                    ])
+              ])
+        ])
+      ],
+      classes: <Class>[],
+      enums: <Enum>[],
+    );
+    final StringBuffer sink = StringBuffer();
+    generateDart(const DartOptions(isNullSafe: true), root, sink);
+    final String code = sink.toString();
+    expect(code, contains('doit(List<int?> arg'));
+  });
+
+  test('host generics return', () {
+    final Root root = Root(
+      apis: <Api>[
+        Api(name: 'Api', location: ApiLocation.host, methods: <Method>[
+          Method(
+              name: 'doit',
+              returnType: Field(
+                  name: 'arg',
+                  dataType: 'List',
+                  isNullable: false,
+                  typeArguments: <TypeArgument>[
+                    TypeArgument(dataType: 'int', isNullable: true)
+                  ]),
+              arguments: <Field>[])
+        ])
+      ],
+      classes: <Class>[],
+      enums: <Enum>[],
+    );
+    final StringBuffer sink = StringBuffer();
+    generateDart(const DartOptions(isNullSafe: true), root, sink);
+    final String code = sink.toString();
+    expect(code, contains('Future<List<int?>> doit('));
+    expect(
+        code,
+        contains(
+            'return (replyMap[\'result\'] as List<Object?>?)!.cast<int?>();'));
+  });
+
+  test('host generics return', () {
+    final Root root = Root(
+      apis: <Api>[
+        Api(name: 'Api', location: ApiLocation.flutter, methods: <Method>[
+          Method(
+              name: 'doit',
+              returnType: Field(
+                  name: 'arg',
+                  dataType: 'List',
+                  isNullable: false,
+                  typeArguments: <TypeArgument>[
+                    TypeArgument(dataType: 'int', isNullable: true)
+                  ]),
+              arguments: <Field>[
+                Field(
+                    name: 'arg',
+                    dataType: 'List',
+                    isNullable: false,
+                    typeArguments: <TypeArgument>[
+                      TypeArgument(dataType: 'int', isNullable: true)
+                    ])
+              ])
+        ])
+      ],
+      classes: <Class>[],
+      enums: <Enum>[],
+    );
+    final StringBuffer sink = StringBuffer();
+    generateDart(const DartOptions(isNullSafe: true), root, sink);
+    final String code = sink.toString();
+    expect(code, contains('List<int?> doit('));
+    expect(
+        code, contains('final List<int?> input = (message as List<int?>?)!'));
+    expect(code, contains('final List<int?> output = api.doit(input)'));
+  });
 }
diff --git a/packages/pigeon/test/java_generator_test.dart b/packages/pigeon/test/java_generator_test.dart
index 4ac1ab63071b..d2048cf4e23f 100644
--- a/packages/pigeon/test/java_generator_test.dart
+++ b/packages/pigeon/test/java_generator_test.dart
@@ -87,9 +87,10 @@ void main() {
       Api(name: 'Api', location: ApiLocation.host, methods: <Method>[
         Method(
           name: 'doSomething',
-          argType: 'Input',
-          isArgNullable: true,
-          returnType: 'Output',
+          arguments: <Field>[
+            Field(name: '', dataType: 'Input', isNullable: false)
+          ],
+          returnType: Field(name: '', dataType: 'Output', isNullable: false),
           isAsynchronous: false,
         )
       ])
@@ -143,9 +144,10 @@ void main() {
       Api(name: 'Api', location: ApiLocation.flutter, methods: <Method>[
         Method(
           name: 'doSomething',
-          argType: 'Input',
-          isArgNullable: false,
-          returnType: 'Output',
+          arguments: <Field>[
+            Field(name: '', dataType: 'Input', isNullable: false)
+          ],
+          returnType: Field(name: '', dataType: 'Output', isNullable: false),
           isAsynchronous: false,
         )
       ])
@@ -170,9 +172,10 @@ void main() {
       Api(name: 'Api', location: ApiLocation.host, methods: <Method>[
         Method(
           name: 'doSomething',
-          argType: 'Input',
-          isArgNullable: false,
-          returnType: 'void',
+          arguments: <Field>[
+            Field(name: '', dataType: 'Input', isNullable: false)
+          ],
+          returnType: Field(name: '', dataType: 'void', isNullable: false),
           isAsynchronous: false,
         )
       ])
@@ -194,9 +197,10 @@ void main() {
       Api(name: 'Api', location: ApiLocation.flutter, methods: <Method>[
         Method(
           name: 'doSomething',
-          argType: 'Input',
-          isArgNullable: false,
-          returnType: 'void',
+          arguments: <Field>[
+            Field(name: '', dataType: 'Input', isNullable: false)
+          ],
+          returnType: Field(name: '', dataType: 'void', isNullable: false),
           isAsynchronous: false,
         )
       ])
@@ -218,9 +222,8 @@ void main() {
       Api(name: 'Api', location: ApiLocation.host, methods: <Method>[
         Method(
           name: 'doSomething',
-          argType: 'void',
-          isArgNullable: false,
-          returnType: 'Output',
+          arguments: <Field>[],
+          returnType: Field(name: '', dataType: 'Output', isNullable: false),
           isAsynchronous: false,
         )
       ])
@@ -242,9 +245,8 @@ void main() {
       Api(name: 'Api', location: ApiLocation.flutter, methods: <Method>[
         Method(
           name: 'doSomething',
-          argType: 'void',
-          isArgNullable: false,
-          returnType: 'Output',
+          arguments: <Field>[],
+          returnType: Field(name: '', dataType: 'Output', isNullable: false),
           isAsynchronous: false,
         )
       ])
@@ -332,9 +334,10 @@ void main() {
       Api(name: 'Api', location: ApiLocation.host, methods: <Method>[
         Method(
           name: 'doSomething',
-          argType: 'Input',
-          isArgNullable: false,
-          returnType: 'Output',
+          arguments: <Field>[
+            Field(name: '', dataType: 'Input', isNullable: false)
+          ],
+          returnType: Field(name: '', dataType: 'Output', isNullable: false),
           isAsynchronous: true,
         )
       ])
@@ -366,9 +369,10 @@ void main() {
       Api(name: 'Api', location: ApiLocation.flutter, methods: <Method>[
         Method(
           name: 'doSomething',
-          argType: 'Input',
-          isArgNullable: false,
-          returnType: 'Output',
+          arguments: <Field>[
+            Field(name: '', dataType: 'Input', isNullable: false)
+          ],
+          returnType: Field(name: '', dataType: 'Output', isNullable: false),
           isAsynchronous: true,
         )
       ])
@@ -441,4 +445,141 @@ void main() {
     final String code = sink.toString();
     expect(code, startsWith('// hello world'));
   });
+
+  test('generics', () {
+    final Class klass = Class(
+      name: 'Foobar',
+      fields: <Field>[
+        Field(
+          name: 'field1',
+          dataType: 'List',
+          isNullable: true,
+          typeArguments: <TypeArgument>[
+            TypeArgument(dataType: 'int', isNullable: true)
+          ],
+        ),
+      ],
+    );
+    final Root root = Root(
+      apis: <Api>[],
+      classes: <Class>[klass],
+      enums: <Enum>[],
+    );
+    final StringBuffer sink = StringBuffer();
+    const JavaOptions javaOptions = JavaOptions(className: 'Messages');
+    generateJava(javaOptions, root, sink);
+    final String code = sink.toString();
+    expect(code, contains('class Foobar'));
+    expect(code, contains('List<Long> field1;'));
+  });
+
+  test('host generics argument', () {
+    final Root root = Root(
+      apis: <Api>[
+        Api(name: 'Api', location: ApiLocation.host, methods: <Method>[
+          Method(
+              name: 'doit',
+              returnType: Field(dataType: 'void', isNullable: false, name: ''),
+              arguments: <Field>[
+                Field(
+                    name: 'arg',
+                    dataType: 'List',
+                    isNullable: false,
+                    typeArguments: <TypeArgument>[
+                      TypeArgument(dataType: 'int', isNullable: true)
+                    ])
+              ])
+        ])
+      ],
+      classes: <Class>[],
+      enums: <Enum>[],
+    );
+    final StringBuffer sink = StringBuffer();
+    const JavaOptions javaOptions = JavaOptions(className: 'Messages');
+    generateJava(javaOptions, root, sink);
+    final String code = sink.toString();
+    expect(code, contains('doit(List<Long> arg'));
+  });
+
+  test('flutter generics argument', () {
+    final Root root = Root(
+      apis: <Api>[
+        Api(name: 'Api', location: ApiLocation.flutter, methods: <Method>[
+          Method(
+              name: 'doit',
+              returnType: Field(dataType: 'void', isNullable: false, name: ''),
+              arguments: <Field>[
+                Field(
+                    name: 'arg',
+                    dataType: 'List',
+                    isNullable: false,
+                    typeArguments: <TypeArgument>[
+                      TypeArgument(dataType: 'int', isNullable: true)
+                    ])
+              ])
+        ])
+      ],
+      classes: <Class>[],
+      enums: <Enum>[],
+    );
+    final StringBuffer sink = StringBuffer();
+    const JavaOptions javaOptions = JavaOptions(className: 'Messages');
+    generateJava(javaOptions, root, sink);
+    final String code = sink.toString();
+    expect(code, contains('doit(List<Long> arg'));
+  });
+
+  test('host generics return', () {
+    final Root root = Root(
+      apis: <Api>[
+        Api(name: 'Api', location: ApiLocation.host, methods: <Method>[
+          Method(
+              name: 'doit',
+              returnType: Field(
+                  name: 'arg',
+                  dataType: 'List',
+                  isNullable: false,
+                  typeArguments: <TypeArgument>[
+                    TypeArgument(dataType: 'int', isNullable: true)
+                  ]),
+              arguments: <Field>[])
+        ])
+      ],
+      classes: <Class>[],
+      enums: <Enum>[],
+    );
+    final StringBuffer sink = StringBuffer();
+    const JavaOptions javaOptions = JavaOptions(className: 'Messages');
+    generateJava(javaOptions, root, sink);
+    final String code = sink.toString();
+    expect(code, contains('List<Long> doit('));
+    expect(code, contains('List<Long> output ='));
+  });
+
+  test('flutter generics return', () {
+    final Root root = Root(
+      apis: <Api>[
+        Api(name: 'Api', location: ApiLocation.flutter, methods: <Method>[
+          Method(
+              name: 'doit',
+              returnType: Field(
+                  name: 'arg',
+                  dataType: 'List',
+                  isNullable: false,
+                  typeArguments: <TypeArgument>[
+                    TypeArgument(dataType: 'int', isNullable: true)
+                  ]),
+              arguments: <Field>[])
+        ])
+      ],
+      classes: <Class>[],
+      enums: <Enum>[],
+    );
+    final StringBuffer sink = StringBuffer();
+    const JavaOptions javaOptions = JavaOptions(className: 'Messages');
+    generateJava(javaOptions, root, sink);
+    final String code = sink.toString();
+    expect(code, contains('doit(Reply<List<Long>> callback)'));
+    expect(code, contains('List<Long> output ='));
+  });
 }
diff --git a/packages/pigeon/test/objc_generator_test.dart b/packages/pigeon/test/objc_generator_test.dart
index 8acf43920cc9..9bca1ab9f988 100644
--- a/packages/pigeon/test/objc_generator_test.dart
+++ b/packages/pigeon/test/objc_generator_test.dart
@@ -115,14 +115,51 @@ void main() {
     expect(code, contains('result.enum1 = [dict[@"enum1"] integerValue];'));
   });
 
+  test('gen one class header with enum', () {
+    final Root root = Root(
+      apis: <Api>[],
+      classes: <Class>[
+        Class(
+          name: 'Foobar',
+          fields: <Field>[
+            Field(
+              name: 'field1',
+              dataType: 'String',
+              isNullable: true,
+            ),
+            Field(
+              name: 'enum1',
+              dataType: 'Enum1',
+              isNullable: true,
+            ),
+          ],
+        ),
+      ],
+      enums: <Enum>[
+        Enum(
+          name: 'Enum1',
+          members: <String>[
+            'one',
+            'two',
+          ],
+        )
+      ],
+    );
+    final StringBuffer sink = StringBuffer();
+    generateObjcHeader(const ObjcOptions(header: 'foo.h'), root, sink);
+    final String code = sink.toString();
+    expect(code, contains('@property(nonatomic, assign) Enum1 enum1'));
+  });
+
   test('gen one api header', () {
     final Root root = Root(apis: <Api>[
       Api(name: 'Api', location: ApiLocation.host, methods: <Method>[
         Method(
             name: 'doSomething',
-            argType: 'Input',
-            isArgNullable: false,
-            returnType: 'Output')
+            arguments: <Field>[
+              Field(name: '', dataType: 'Input', isNullable: false)
+            ],
+            returnType: Field(name: '', dataType: 'Output', isNullable: false))
       ])
     ], classes: <Class>[
       Class(name: 'Input', fields: <Field>[
@@ -155,9 +192,10 @@ void main() {
       Api(name: 'Api', location: ApiLocation.host, methods: <Method>[
         Method(
             name: 'doSomething',
-            argType: 'Input',
-            isArgNullable: false,
-            returnType: 'Output')
+            arguments: <Field>[
+              Field(name: '', dataType: 'Input', isNullable: false)
+            ],
+            returnType: Field(name: '', dataType: 'Output', isNullable: false))
       ])
     ], classes: <Class>[
       Class(name: 'Input', fields: <Field>[
@@ -352,9 +390,10 @@ void main() {
       Api(name: 'Api', location: ApiLocation.host, methods: <Method>[
         Method(
             name: 'doSomething',
-            argType: 'Input',
-            isArgNullable: false,
-            returnType: 'Nested')
+            arguments: <Field>[
+              Field(name: '', dataType: 'Input', isNullable: false)
+            ],
+            returnType: Field(name: '', dataType: 'Nested', isNullable: false))
       ])
     ], classes: <Class>[
       Class(name: 'Input', fields: <Field>[
@@ -385,9 +424,10 @@ void main() {
       Api(name: 'Api', location: ApiLocation.host, methods: <Method>[
         Method(
             name: 'doSomething',
-            argType: 'Input',
-            isArgNullable: false,
-            returnType: 'Nested')
+            arguments: <Field>[
+              Field(name: '', dataType: 'Input', isNullable: false)
+            ],
+            returnType: Field(name: '', dataType: 'Nested', isNullable: false))
       ])
     ], classes: <Class>[
       Class(name: 'Input', fields: <Field>[
@@ -418,9 +458,10 @@ void main() {
       Api(name: 'Api', location: ApiLocation.flutter, methods: <Method>[
         Method(
             name: 'doSomething',
-            argType: 'Input',
-            isArgNullable: false,
-            returnType: 'Output')
+            arguments: <Field>[
+              Field(name: '', dataType: 'Input', isNullable: false)
+            ],
+            returnType: Field(name: '', dataType: 'Output', isNullable: false))
       ])
     ], classes: <Class>[
       Class(name: 'Input', fields: <Field>[
@@ -454,9 +495,10 @@ void main() {
       Api(name: 'Api', location: ApiLocation.flutter, methods: <Method>[
         Method(
             name: 'doSomething',
-            argType: 'Input',
-            isArgNullable: false,
-            returnType: 'Output')
+            arguments: <Field>[
+              Field(name: '', dataType: 'Input', isNullable: false)
+            ],
+            returnType: Field(name: '', dataType: 'Output', isNullable: false))
       ])
     ], classes: <Class>[
       Class(name: 'Input', fields: <Field>[
@@ -486,9 +528,10 @@ void main() {
       Api(name: 'Api', location: ApiLocation.host, methods: <Method>[
         Method(
             name: 'doSomething',
-            argType: 'Input',
-            isArgNullable: false,
-            returnType: 'void')
+            arguments: <Field>[
+              Field(name: '', dataType: 'Input', isNullable: false)
+            ],
+            returnType: Field(name: '', dataType: 'void', isNullable: false))
       ])
     ], classes: <Class>[
       Class(name: 'Input', fields: <Field>[
@@ -511,9 +554,10 @@ void main() {
       Api(name: 'Api', location: ApiLocation.host, methods: <Method>[
         Method(
             name: 'doSomething',
-            argType: 'Input',
-            isArgNullable: false,
-            returnType: 'void')
+            arguments: <Field>[
+              Field(name: '', dataType: 'Input', isNullable: false)
+            ],
+            returnType: Field(name: '', dataType: 'void', isNullable: false))
       ])
     ], classes: <Class>[
       Class(name: 'Input', fields: <Field>[
@@ -538,9 +582,10 @@ void main() {
       Api(name: 'Api', location: ApiLocation.flutter, methods: <Method>[
         Method(
             name: 'doSomething',
-            argType: 'Input',
-            isArgNullable: false,
-            returnType: 'void')
+            arguments: <Field>[
+              Field(name: '', dataType: 'Input', isNullable: false)
+            ],
+            returnType: Field(name: '', dataType: 'void', isNullable: false))
       ])
     ], classes: <Class>[
       Class(name: 'Input', fields: <Field>[
@@ -563,9 +608,10 @@ void main() {
       Api(name: 'Api', location: ApiLocation.flutter, methods: <Method>[
         Method(
             name: 'doSomething',
-            argType: 'Input',
-            isArgNullable: false,
-            returnType: 'void')
+            arguments: <Field>[
+              Field(name: '', dataType: 'Input', isNullable: false)
+            ],
+            returnType: Field(name: '', dataType: 'void', isNullable: false))
       ])
     ], classes: <Class>[
       Class(name: 'Input', fields: <Field>[
@@ -589,9 +635,8 @@ void main() {
       Api(name: 'Api', location: ApiLocation.host, methods: <Method>[
         Method(
             name: 'doSomething',
-            argType: 'void',
-            isArgNullable: false,
-            returnType: 'Output')
+            arguments: <Field>[],
+            returnType: Field(name: '', dataType: 'Output', isNullable: false))
       ])
     ], classes: <Class>[
       Class(name: 'Output', fields: <Field>[
@@ -614,9 +659,8 @@ void main() {
       Api(name: 'Api', location: ApiLocation.host, methods: <Method>[
         Method(
             name: 'doSomething',
-            argType: 'void',
-            isArgNullable: false,
-            returnType: 'Output')
+            arguments: <Field>[],
+            returnType: Field(name: '', dataType: 'Output', isNullable: false))
       ])
     ], classes: <Class>[
       Class(name: 'Output', fields: <Field>[
@@ -639,9 +683,8 @@ void main() {
       Api(name: 'Api', location: ApiLocation.flutter, methods: <Method>[
         Method(
             name: 'doSomething',
-            argType: 'void',
-            isArgNullable: false,
-            returnType: 'Output')
+            arguments: <Field>[],
+            returnType: Field(name: '', dataType: 'Output', isNullable: false))
       ])
     ], classes: <Class>[
       Class(name: 'Output', fields: <Field>[
@@ -667,9 +710,8 @@ void main() {
       Api(name: 'Api', location: ApiLocation.flutter, methods: <Method>[
         Method(
             name: 'doSomething',
-            argType: 'void',
-            isArgNullable: false,
-            returnType: 'Output')
+            arguments: <Field>[],
+            returnType: Field(name: '', dataType: 'Output', isNullable: false))
       ])
     ], classes: <Class>[
       Class(name: 'Output', fields: <Field>[
@@ -730,9 +772,10 @@ void main() {
       Api(name: 'Api', location: ApiLocation.host, methods: <Method>[
         Method(
             name: 'doSomething',
-            argType: 'Input',
-            isArgNullable: false,
-            returnType: 'void',
+            arguments: <Field>[
+              Field(name: '', dataType: 'Input', isNullable: false)
+            ],
+            returnType: Field(name: '', dataType: 'void', isNullable: false),
             isAsynchronous: true)
       ])
     ], classes: <Class>[
@@ -766,9 +809,10 @@ void main() {
       Api(name: 'Api', location: ApiLocation.host, methods: <Method>[
         Method(
             name: 'doSomething',
-            argType: 'Input',
-            isArgNullable: false,
-            returnType: 'Output',
+            arguments: <Field>[
+              Field(name: '', dataType: 'Input', isNullable: false)
+            ],
+            returnType: Field(name: '', dataType: 'Output', isNullable: false),
             isAsynchronous: true)
       ])
     ], classes: <Class>[
@@ -802,9 +846,8 @@ void main() {
       Api(name: 'Api', location: ApiLocation.host, methods: <Method>[
         Method(
             name: 'doSomething',
-            argType: 'void',
-            isArgNullable: false,
-            returnType: 'Output',
+            arguments: <Field>[],
+            returnType: Field(name: '', dataType: 'Output', isNullable: false),
             isAsynchronous: true)
       ])
     ], classes: <Class>[
@@ -831,9 +874,8 @@ void main() {
       Api(name: 'Api', location: ApiLocation.host, methods: <Method>[
         Method(
             name: 'doSomething',
-            argType: 'void',
-            isArgNullable: false,
-            returnType: 'void',
+            arguments: <Field>[],
+            returnType: Field(name: '', dataType: 'void', isNullable: false),
             isAsynchronous: true)
       ])
     ], classes: <Class>[], enums: <Enum>[]);
@@ -852,9 +894,10 @@ void main() {
       Api(name: 'Api', location: ApiLocation.host, methods: <Method>[
         Method(
             name: 'doSomething',
-            argType: 'Input',
-            isArgNullable: false,
-            returnType: 'Output',
+            arguments: <Field>[
+              Field(name: '', dataType: 'Input', isNullable: false)
+            ],
+            returnType: Field(name: '', dataType: 'Output', isNullable: false),
             isAsynchronous: true)
       ])
     ], classes: <Class>[
@@ -888,9 +931,10 @@ void main() {
       Api(name: 'Api', location: ApiLocation.host, methods: <Method>[
         Method(
             name: 'doSomething',
-            argType: 'Input',
-            isArgNullable: false,
-            returnType: 'void',
+            arguments: <Field>[
+              Field(name: '', dataType: 'Input', isNullable: false)
+            ],
+            returnType: Field(name: '', dataType: 'void', isNullable: false),
             isAsynchronous: true)
       ])
     ], classes: <Class>[
@@ -924,9 +968,8 @@ void main() {
       Api(name: 'Api', location: ApiLocation.host, methods: <Method>[
         Method(
             name: 'doSomething',
-            argType: 'void',
-            isArgNullable: false,
-            returnType: 'void',
+            arguments: <Field>[],
+            returnType: Field(name: '', dataType: 'void', isNullable: false),
             isAsynchronous: true)
       ])
     ], classes: <Class>[], enums: <Enum>[]);
@@ -943,9 +986,8 @@ void main() {
       Api(name: 'Api', location: ApiLocation.host, methods: <Method>[
         Method(
             name: 'doSomething',
-            argType: 'void',
-            isArgNullable: false,
-            returnType: 'Output',
+            arguments: <Field>[],
+            returnType: Field(name: '', dataType: 'Output', isNullable: false),
             isAsynchronous: true)
       ])
     ], classes: <Class>[
@@ -1000,4 +1042,209 @@ void main() {
     final String code = sink.toString();
     expect(code, startsWith('// hello world'));
   });
+
+  test('field generics', () {
+    final Class klass = Class(
+      name: 'Foobar',
+      fields: <Field>[
+        Field(
+          name: 'field1',
+          dataType: 'List',
+          isNullable: true,
+          typeArguments: <TypeArgument>[
+            TypeArgument(dataType: 'int', isNullable: true)
+          ],
+        ),
+      ],
+    );
+    final Root root = Root(
+      apis: <Api>[],
+      classes: <Class>[klass],
+      enums: <Enum>[],
+    );
+    final StringBuffer sink = StringBuffer();
+    generateObjcHeader(
+        const ObjcOptions(header: 'foo.h', prefix: 'ABC'), root, sink);
+    final String code = sink.toString();
+    expect(code, contains('NSArray<NSNumber *> * field1'));
+  });
+
+  test('host generics argument', () {
+    final Root root = Root(
+      apis: <Api>[
+        Api(name: 'Api', location: ApiLocation.host, methods: <Method>[
+          Method(
+              name: 'doit',
+              returnType: Field(dataType: 'void', isNullable: false, name: ''),
+              arguments: <Field>[
+                Field(
+                    name: 'arg',
+                    dataType: 'List',
+                    isNullable: false,
+                    typeArguments: <TypeArgument>[
+                      TypeArgument(dataType: 'int', isNullable: true)
+                    ])
+              ])
+        ])
+      ],
+      classes: <Class>[],
+      enums: <Enum>[],
+    );
+    {
+      final StringBuffer sink = StringBuffer();
+      generateObjcHeader(
+          const ObjcOptions(header: 'foo.h', prefix: 'ABC'), root, sink);
+      final String code = sink.toString();
+      expect(code, contains('doit:(NSArray<NSNumber *>*)input'));
+    }
+    {
+      final StringBuffer sink = StringBuffer();
+      generateObjcSource(
+          const ObjcOptions(header: 'foo.h', prefix: 'ABC'), root, sink);
+      final String code = sink.toString();
+      expect(code, contains('NSArray<NSNumber *> *input = message'));
+    }
+  });
+
+  test('flutter generics argument', () {
+    final Root root = Root(
+      apis: <Api>[
+        Api(name: 'Api', location: ApiLocation.flutter, methods: <Method>[
+          Method(
+              name: 'doit',
+              returnType: Field(dataType: 'void', isNullable: false, name: ''),
+              arguments: <Field>[
+                Field(
+                    name: 'arg',
+                    dataType: 'List',
+                    isNullable: false,
+                    typeArguments: <TypeArgument>[
+                      TypeArgument(dataType: 'int', isNullable: true)
+                    ])
+              ])
+        ])
+      ],
+      classes: <Class>[],
+      enums: <Enum>[],
+    );
+    {
+      final StringBuffer sink = StringBuffer();
+      generateObjcHeader(
+          const ObjcOptions(header: 'foo.h', prefix: 'ABC'), root, sink);
+      final String code = sink.toString();
+      expect(code, contains('doit:(NSArray<NSNumber *>*)input'));
+    }
+    {
+      final StringBuffer sink = StringBuffer();
+      generateObjcSource(
+          const ObjcOptions(header: 'foo.h', prefix: 'ABC'), root, sink);
+      final String code = sink.toString();
+      expect(code, contains('doit:(NSArray<NSNumber *>*)input'));
+    }
+  });
+
+  test('host nested generic argument', () {
+    final Root root = Root(
+      apis: <Api>[
+        Api(name: 'Api', location: ApiLocation.host, methods: <Method>[
+          Method(
+              name: 'doit',
+              returnType: Field(dataType: 'void', isNullable: false, name: ''),
+              arguments: <Field>[
+                Field(
+                    name: 'arg',
+                    dataType: 'List',
+                    isNullable: false,
+                    typeArguments: <TypeArgument>[
+                      TypeArgument(
+                          dataType: 'List',
+                          isNullable: true,
+                          typeArguments: <TypeArgument>[
+                            TypeArgument(dataType: 'bool', isNullable: true)
+                          ]),
+                    ])
+              ])
+        ])
+      ],
+      classes: <Class>[],
+      enums: <Enum>[],
+    );
+    {
+      final StringBuffer sink = StringBuffer();
+      generateObjcHeader(
+          const ObjcOptions(header: 'foo.h', prefix: 'ABC'), root, sink);
+      final String code = sink.toString();
+      expect(code, contains('doit:(NSArray<NSArray<NSNumber *> *>*)input'));
+    }
+  });
+
+  test('host generics return', () {
+    final Root root = Root(
+      apis: <Api>[
+        Api(name: 'Api', location: ApiLocation.host, methods: <Method>[
+          Method(
+              name: 'doit',
+              returnType: Field(
+                  name: 'arg',
+                  dataType: 'List',
+                  isNullable: false,
+                  typeArguments: <TypeArgument>[
+                    TypeArgument(dataType: 'int', isNullable: true)
+                  ]),
+              arguments: <Field>[])
+        ])
+      ],
+      classes: <Class>[],
+      enums: <Enum>[],
+    );
+    {
+      final StringBuffer sink = StringBuffer();
+      generateObjcHeader(
+          const ObjcOptions(header: 'foo.h', prefix: 'ABC'), root, sink);
+      final String code = sink.toString();
+      expect(code, contains('-(nullable NSArray<NSNumber *> *)doit:'));
+    }
+    {
+      final StringBuffer sink = StringBuffer();
+      generateObjcSource(
+          const ObjcOptions(header: 'foo.h', prefix: 'ABC'), root, sink);
+      final String code = sink.toString();
+      expect(code, contains('NSArray<NSNumber *> *output ='));
+    }
+  });
+
+  test('host generics return', () {
+    final Root root = Root(
+      apis: <Api>[
+        Api(name: 'Api', location: ApiLocation.flutter, methods: <Method>[
+          Method(
+              name: 'doit',
+              returnType: Field(
+                  name: 'arg',
+                  dataType: 'List',
+                  isNullable: false,
+                  typeArguments: <TypeArgument>[
+                    TypeArgument(dataType: 'int', isNullable: true)
+                  ]),
+              arguments: <Field>[])
+        ])
+      ],
+      classes: <Class>[],
+      enums: <Enum>[],
+    );
+    {
+      final StringBuffer sink = StringBuffer();
+      generateObjcHeader(
+          const ObjcOptions(header: 'foo.h', prefix: 'ABC'), root, sink);
+      final String code = sink.toString();
+      expect(code, contains('doit:(void(^)(NSArray<NSNumber *>*'));
+    }
+    {
+      final StringBuffer sink = StringBuffer();
+      generateObjcSource(
+          const ObjcOptions(header: 'foo.h', prefix: 'ABC'), root, sink);
+      final String code = sink.toString();
+      expect(code, contains('doit:(void(^)(NSArray<NSNumber *>*'));
+    }
+  });
 }
diff --git a/packages/pigeon/test/pigeon_lib_test.dart b/packages/pigeon/test/pigeon_lib_test.dart
index 6aba0a002f30..780c2c97acab 100644
--- a/packages/pigeon/test/pigeon_lib_test.dart
+++ b/packages/pigeon/test/pigeon_lib_test.dart
@@ -93,8 +93,8 @@ abstract class Api1 {
     expect(root.apis[0].name, equals('Api1'));
     expect(root.apis[0].methods.length, equals(1));
     expect(root.apis[0].methods[0].name, equals('doit'));
-    expect(root.apis[0].methods[0].argType, equals('Input1'));
-    expect(root.apis[0].methods[0].returnType, equals('Output1'));
+    expect(root.apis[0].methods[0].arguments[0].dataType, equals('Input1'));
+    expect(root.apis[0].methods[0].returnType.dataType, equals('Output1'));
 
     Class? input;
     Class? output;
@@ -241,7 +241,7 @@ abstract class VoidApi {
     expect(results.root.apis.length, equals(1));
     expect(results.root.apis[0].methods.length, equals(1));
     expect(results.root.apis[0].name, equals('VoidApi'));
-    expect(results.root.apis[0].methods[0].returnType, equals('void'));
+    expect(results.root.apis[0].methods[0].returnType.dataType, equals('void'));
   });
 
   test('void arg host api', () {
@@ -260,8 +260,9 @@ abstract class VoidArgApi {
     expect(results.root.apis.length, equals(1));
     expect(results.root.apis[0].methods.length, equals(1));
     expect(results.root.apis[0].name, equals('VoidArgApi'));
-    expect(results.root.apis[0].methods[0].returnType, equals('Output1'));
-    expect(results.root.apis[0].methods[0].argType, equals('void'));
+    expect(
+        results.root.apis[0].methods[0].returnType.dataType, equals('Output1'));
+    expect(results.root.apis[0].methods[0].arguments.isEmpty, isTrue);
   });
 
   test('mockDartClass', () {
@@ -537,38 +538,155 @@ abstract class Api {
     expect(parseResults.errors.length, 0);
   });
 
-  test('error with generics', () {
+  test('error with static field', () {
     const String code = '''
-class WithTemplate {
-  List<int>? list;
+class WithStaticField {
+  static int? x;
+  int? y;
 }
 
 @HostApi()
-abstract class WithTemplateApi {
-  void doit(WithTemplate withTemplate);
+abstract class WithStaticFieldApi {
+  void doit(WithStaticField withTemplate);
 }
 ''';
     final ParseResults parseResult = _parseSource(code);
     expect(parseResult.errors.length, equals(1));
-    expect(parseResult.errors[0].message, contains('Generic fields'));
+    expect(parseResult.errors[0].message, contains('static field'));
     expect(parseResult.errors[0].lineNumber, isNotNull);
   });
 
-  test('error with static field', () {
+  test('parse generics', () {
     const String code = '''
-class WithStaticField {
-  static int? x;
-  int? y;
+class Foo {
+  List<int?>? list;
 }
 
 @HostApi()
-abstract class WithStaticFieldApi {
-  void doit(WithStaticField withTemplate);
+abstract class Api {
+  void doit(Foo foo);
+}
+''';
+    final ParseResults parseResult = _parseSource(code);
+    expect(parseResult.errors.length, equals(0));
+    final Field field = parseResult.root.classes[0].fields[0];
+    expect(field.typeArguments!.length, 1);
+    expect(field.typeArguments![0].dataType, 'int');
+  });
+
+  test('parse recursive generics', () {
+    const String code = '''
+class Foo {
+  List<List<int?>?>? list;
+}
+
+@HostApi()
+abstract class Api {
+  void doit(Foo foo);
+}
+''';
+    final ParseResults parseResult = _parseSource(code);
+    expect(parseResult.errors.length, equals(0));
+    final Field field = parseResult.root.classes[0].fields[0];
+    expect(field.typeArguments!.length, 1);
+    expect(field.typeArguments![0].dataType, 'List');
+    expect(field.typeArguments![0].typeArguments![0].dataType, 'int');
+  });
+
+  test('error nonnull type argument', () {
+    const String code = '''
+class Foo {
+  List<int> list;
+}
+
+@HostApi()
+abstract class Api {
+  void doit(Foo foo);
 }
 ''';
     final ParseResults parseResult = _parseSource(code);
     expect(parseResult.errors.length, equals(1));
-    expect(parseResult.errors[0].message, contains('static field'));
-    expect(parseResult.errors[0].lineNumber, isNotNull);
+    expect(parseResult.errors[0].message,
+        contains('Generic type arguments must be nullable'));
+    expect(parseResult.errors[0].message, contains('"list"'));
+    expect(parseResult.errors[0].lineNumber, 2);
+  });
+
+  test('return type generics', () {
+    const String code = '''
+@HostApi()
+abstract class Api {
+  List<double?> doit();
+}
+''';
+    final ParseResults parseResult = _parseSource(code);
+    expect(parseResult.root.apis[0].methods[0].returnType.dataType, 'List');
+    expect(
+        parseResult
+            .root.apis[0].methods[0].returnType.typeArguments![0].dataType,
+        'double');
+    expect(
+        parseResult
+            .root.apis[0].methods[0].returnType.typeArguments![0].isNullable,
+        isTrue);
+  });
+
+  test('argument generics', () {
+    const String code = '''
+@HostApi()
+abstract class Api {
+  void doit(List<double?> value);
+}
+''';
+    final ParseResults parseResult = _parseSource(code);
+    expect(parseResult.root.apis[0].methods[0].arguments[0].dataType, 'List');
+    expect(
+        parseResult
+            .root.apis[0].methods[0].arguments[0].typeArguments![0].dataType,
+        'double');
+    expect(
+        parseResult
+            .root.apis[0].methods[0].arguments[0].typeArguments![0].isNullable,
+        isTrue);
+  });
+
+  test('map generics', () {
+    const String code = '''
+class Foo {
+  Map<String?, int?> map;
+}
+
+@HostApi()
+abstract class Api {
+  void doit(Foo foo);
+}
+''';
+    final ParseResults parseResult = _parseSource(code);
+    final Field field = parseResult.root.classes[0].fields[0];
+    expect(field.typeArguments!.length, 2);
+    expect(field.typeArguments![0].dataType, 'String');
+    expect(field.typeArguments![1].dataType, 'int');
+  });
+
+  test('two arguments', () {
+    const String code = '''
+class Input {
+  String? input;
+}
+
+@HostApi()
+abstract class Api {
+  void method(Input input1, Input input2);
+}
+''';
+    final ParseResults results = _parseSource(code);
+    expect(results.errors.length, 1);
+    expect(results.errors[0].lineNumber, 7);
+    expect(results.errors[0].message, contains('Multiple arguments'));
+    // TODO(gaaclarke): Make this not an error, https://github.com/flutter/flutter/issues/86971.
+    // expect(results.root.apis.length, 1);
+    // expect(results.root.apis[0].methods.length, equals(1));
+    // expect(results.root.apis[0].methods[0].name, equals('method'));
+    // expect(results.root.apis[0].methods[0].arguments.length, 2);
   });
 }