add InheritedWidget macro example and fix up FunctionalWidget

working/macros/example/benchmark/src/functional_widget.dart

@@ -12,8 +12,9 @@ Future<void> runBenchmarks(MacroExecutor executor, Uri macroUri) async {
       'int': intIdentifier,
       'String': stringIdentifier,
     },
-    Uri.parse('package:flutter/flutter.dart'): {
+    Uri.parse('package:flutter/widgets.dart'): {
       'BuildContext': buildContextIdentifier,
+      'StatelessWidget': statelessWidgetIdentifier,
       'Widget': widgetIdentifier,
     }
   });
@@ -67,6 +68,8 @@ class FunctionalWidgetTypesPhaseBenchmark extends AsyncBenchmarkBase {
 
 final buildContextIdentifier =
     IdentifierImpl(id: RemoteInstance.uniqueId, name: 'BuildContext');
+final statelessWidgetIdentifier =
+    IdentifierImpl(id: RemoteInstance.uniqueId, name: 'StatelessWidget');
 final buildContextType = NamedTypeAnnotationImpl(
     id: RemoteInstance.uniqueId,
     isNullable: false,

working/macros/example/lib/functional_widget.dart

@@ -5,6 +5,14 @@
 // There is no public API exposed yet, the in-progress API lives here.
 import 'package:_fe_analyzer_shared/src/macros/api.dart';
 
+/// A macro that annotates a function, which becomes the build method for a
+/// generated stateless widget.
+///
+/// The function must have at least one positional parameter, which is of type
+/// BuildContext (and this must be the first parameter).
+///
+/// Any additional function parameters are turned into fields on the stateless
+/// widget.
 macro class FunctionalWidget implements FunctionTypesMacro {
   final Identifier? widgetIdentifier;
 
@@ -15,8 +23,8 @@ macro class FunctionalWidget implements FunctionTypesMacro {
       this.widgetIdentifier});
 
   @override
-  void buildTypesForFunction(
-      FunctionDeclaration function, TypeBuilder builder) {
+  Future<void> buildTypesForFunction(
+      FunctionDeclaration function, TypeBuilder builder) async {
     if (!function.identifier.name.startsWith('_')) {
       throw ArgumentError(
           'FunctionalWidget should only be used on private declarations');
@@ -36,10 +44,19 @@ macro class FunctionalWidget implements FunctionTypesMacro {
         function.identifier.name
             .replaceRange(0, 2, function.identifier.name[1].toUpperCase());
     var positionalFieldParams = function.positionalParameters.skip(1);
+    // ignore: deprecated_member_use
+    var statelessWidget = await builder.resolveIdentifier(
+        Uri.parse('package:flutter/widgets.dart'), 'StatelessWidget');
+    // ignore: deprecated_member_use
+    var buildContext = await builder.resolveIdentifier(
+        Uri.parse('package:flutter/widgets.dart'), 'BuildContext');
+    // ignore: deprecated_member_use
+    var widget = await builder.resolveIdentifier(
+        Uri.parse('package:flutter/widgets.dart'), 'Widget');
     builder.declareType(
         widgetName,
         DeclarationCode.fromParts([
-          'class $widgetName extends StatelessWidget {',
+          'class $widgetName extends ', statelessWidget, ' {',
           // Fields
           for (var param
               in positionalFieldParams.followedBy(function.namedParameters))
@@ -57,13 +74,14 @@ macro class FunctionalWidget implements FunctionTypesMacro {
           '{',
           for (var param in function.namedParameters)
             '${param.isRequired ? 'required ' : ''}this.${param.identifier.name}, ',
-          'Key? key,',
-          '}',
-          ') : super(key: key);',
+          'super.key,',
+          '});',
           // Build method
-          '''
-          @override
-          Widget build(BuildContext context) => ''',
+          '@override ',
+          widget,
+          ' build(',
+          buildContext,
+          ' context) => ',
           function.identifier,
           '(context, ',
           for (var param in positionalFieldParams) '${param.identifier.name}, ',

working/macros/example/lib/inherited_widget.dart

@@ -0,0 +1,97 @@
+// Copyright (c) 2023, the Dart project authors. Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+// There is no public API exposed yet, the in-progress API lives here.
+import 'package:_fe_analyzer_shared/src/macros/api.dart';
+
+/// A macro that annotates a class and turns it into an inherited widget.
+///
+/// This will fill in any "holes" that do not have custom implementations,
+/// specifically the following items will be added if they don't exist:
+///
+/// - Make the class extend `InheritedWidget`.
+/// - Add a constructor that will initialize any fields that are defined, and
+///   take `key` and `child` parameters which it forwards to the super
+///   constructor.
+/// - Add static `of` and `maybeOf` methods which take a build context and
+///   return an instance of this class using `dependOnIheritedWidgetOfExactType`.
+/// - Add an `updateShouldNotify` method which does checks for equality of all
+///   fields.
+macro class InheritedWidget implements ClassTypesMacro, ClassDeclarationsMacro {
+  const InheritedWidget();
+
+  @override
+  void buildTypesForClass(
+      ClassDeclaration clazz, ClassTypeBuilder builder) {
+    if (clazz.superclass != null) return;
+    // TODO: Add `extends InheritedWidget` once we have an API for that.
+  }
+
+  @override
+  Future<void> buildDeclarationsForClass(IntrospectableClassDeclaration clazz, MemberDeclarationBuilder builder) async {
+    final fields = await builder.fieldsOf(clazz);
+    final methods = await builder.methodsOf(clazz);
+    if (!methods.any((method) => method is ConstructorDeclaration)) {
+      builder.declareInType(DeclarationCode.fromParts([
+            'const ${clazz.identifier.name}(',
+            '{',
+            for (var field in fields)...[
+                field.type.isNullable ? '' : 'required ',
+              field.identifier,
+              ',',
+            ],
+            'super.key,',
+            'required super.child,',
+            '});',
+      ]));
+    }
+
+    final buildContext =
+      // ignore: deprecated_member_use
+      await builder.resolveIdentifier(Uri.parse('package:flutter/widgets.dart'), 'BuildContext');
+    if (!methods.any((method) => method.identifier.name == "maybeOf")) {
+      builder.declareInType(DeclarationCode.fromParts([
+        'static ',
+        clazz.identifier,
+        '? maybeOf(',
+        buildContext,
+        ' context) => context.dependOnInheritedWidgetOfExactType<',
+        clazz.identifier,
+        '>();',
+      ]));
+    }
+
+    if (!methods.any((method) => method.identifier.name == "of")) {
+      builder.declareInType(DeclarationCode.fromParts([
+        'static ',
+        clazz.identifier,
+        ' of(',
+        buildContext,
+        ''' context) {
+          final result = this.maybeOf(context);
+          assert(result != null, 'No ${clazz.identifier.name} found in context');
+          return result!;
+        }''',
+      ]));
+    }
+
+    if (!methods.any((method) => method.identifier.name == 'updateShouldNotify')) {
+      // ignore: deprecated_member_use
+      final override = await builder.resolveIdentifier(
+          Uri.parse('package:meta/meta.dart'), 'override');
+      builder.declareInType(DeclarationCode.fromParts([
+        '@',
+        override,
+        ' bool updateShouldNotify(',
+        clazz.identifier,
+        ' oldWidget) =>',
+        ...[
+          for (var field in fields)
+            'oldWidget.${field.identifier.name} != this.${field.identifier.name}',
+        ].joinAsCode(' || '),
+        ';',
+      ]));
+    }
+  }
+}