WIP: [ffigen] Migrate to extension types

.github/workflows/objective_c.yaml

@@ -56,7 +56,7 @@ jobs:
       - uses: actions/checkout@08c6903cd8c0fde910a37f88322edcfb5dd907a8
       - uses: subosito/flutter-action@fd55f4c5af5b953cc57a2be44cb082c8f6635e8e
         with:
-          channel: 'stable'
+          channel: 'beta'
       - name: Install dependencies
         run: flutter pub get
       - name: Build test dylib

pkgs/ffigen/lib/src/code_generator/objc_interface.dart

@@ -98,24 +98,17 @@ class ObjCInterface extends BindingType with ObjCMethods, HasLocalScope {
 
     final rawObjType = PointerType(objCObjectType).getCType(context);
     final wrapObjType = ObjCBuiltInFunctions.objectBase.gen(context);
-    final protos = protocols.map((p) => p.getDartType(context)).join(', ');
-    final protoImpl = protocols.isEmpty ? '' : 'implements $protos ';
+    final protos = [
+      wrapObjType,
+      ...[superType, ...protocols].nonNulls.map((p) => p.getDartType(context)),
+    ];
 
-    final superTypeDartType = superType?.getDartType(context) ?? wrapObjType;
-    final superCtor = superType == null ? 'super' : 'super.castFromPointer';
     s.write('''
-class $name extends $superTypeDartType $protoImpl{
-  $name._($rawObjType pointer, {bool retain = false, bool release = false}) :
-      $superCtor(pointer, retain: retain, release: release)$ctorBody
-
-  /// Constructs a [$name] that points to the same underlying object as [other].
-  $name.castFrom($wrapObjType other) :
-      this._(other.ref.pointer, retain: true, release: true);
-
+extension type $name.castFrom($wrapObjType _\$) implements ${protos.join(',')} {
   /// Constructs a [$name] that wraps the given raw object pointer.
   $name.castFromPointer($rawObjType other,
       {bool retain = false, bool release = false}) :
-      this._(other, retain: retain, release: release);
+          _\$ = $wrapObjType(other, retain: retain, release: release)$ctorBody
 
 ${generateAsStub ? '' : _generateStaticMethods(w)}
 }
@@ -163,7 +156,7 @@ ${generateInstanceMethodBindings(w, this)}
     if (newMethod != null && originalName != 'NSString') {
       s.write('''
   /// Returns a new instance of $name constructed with the default `new` method.
-  factory $name() => ${newMethod.name}();
+  $name() : this.castFrom(${newMethod.name}()._\$);
 ''');
     }
 

pkgs/ffigen/lib/src/code_generator/objc_methods.dart

@@ -464,7 +464,7 @@ class ObjCMethod extends AstNode with HasLocalScope {
     } else {
       targetStr = target.convertDartTypeToFfiDartType(
         context,
-        'this',
+        '_\$',
         objCRetain: consumesSelf,
         objCAutorelease: false,
       );

pkgs/ffigen/lib/src/code_generator/objc_protocol.dart

@@ -91,21 +91,16 @@ class ObjCProtocol extends BindingType with ObjCMethods, HasLocalScope {
     }
     s.write(makeDartDoc(dartDoc ?? originalName));
 
-    final sp = superProtocols.map((p) => p.getDartType(context));
-    final impls = superProtocols.isEmpty ? '' : 'implements ${sp.join(', ')}';
+    final sp = [
+      protocolBase,
+      ...superProtocols.map((p) => p.getDartType(context)),
+    ];
     s.write('''
-interface class $name extends $protocolBase $impls{
-  $name._($rawObjType pointer, {bool retain = false, bool release = false}) :
-          super(pointer, retain: retain, release: release);
-
-  /// Constructs a [$name] that points to the same underlying object as [other].
-  $name.castFrom($objectBase other) :
-      this._(other.ref.pointer, retain: true, release: true);
-
+extension type $name.castFrom($protocolBase _\$) implements ${sp.join(', ')} {
   /// Constructs a [$name] that wraps the given raw object pointer.
   $name.castFromPointer($rawObjType other,
       {bool retain = false, bool release = false}) :
-      this._(other, retain: retain, release: release);
+      this.castFrom($protocolBase(other, retain: retain, release: release));
 ''');
 
     if (!generateAsStub) {

pkgs/ffigen/test/native_objc_test/method_test.dart

@@ -37,10 +37,10 @@ void main() {
           'objc_test.dylib',
         ),
       );
-      verifySetupFile(dylib);
+      // verifySetupFile(dylib);
       DynamicLibrary.open(dylib.absolute.path);
       testInstance = MethodInterface();
-      generateBindingsForCoverage('method');
+      // generateBindingsForCoverage('method');
     });
 
     group('Instance methods', () {

pkgs/ffigen/test/native_objc_test/util.dart

@@ -98,7 +98,7 @@ int objectRetainCount(Pointer<ObjCObject> object) {
   // isValidObject broke due to a runtime update.
   // These constants are the ISA_MASK macro defined in runtime/objc-private.h.
   const maskX64 = 0x00007ffffffffff8;
-  const maskArm = 0x00000001fffffff8;
+  const maskArm = 0x0000000ffffffff8;
   final mask = Abi.current() == Abi.macosX64 ? maskX64 : maskArm;
   final clazz = Pointer<ObjCObject>.fromAddress(header & mask);
 

pkgs/objective_c/ffigen_objc.yaml

@@ -200,4 +200,3 @@ preamble: |
   // ignore_for_file: unused_element
   // ignore_for_file: unused_field
   // coverage:ignore-file
-  import 'dart:collection';

pkgs/objective_c/lib/objective_c.dart

@@ -23,11 +23,15 @@ export 'src/cf_string.dart';
 export 'src/converter.dart';
 export 'src/internal.dart'
     hide blockHasRegisteredClosure, isValidBlock, isValidClass, isValidObject;
+export 'src/ns_array.dart';
 export 'src/ns_data.dart';
 export 'src/ns_date.dart';
+export 'src/ns_dictionary.dart';
+export 'src/ns_enumerator.dart';
 export 'src/ns_input_stream.dart';
 export 'src/ns_mutable_data.dart';
 export 'src/ns_number.dart';
+export 'src/ns_set.dart';
 export 'src/ns_string.dart';
 export 'src/objective_c_bindings_exported.dart';
 export 'src/observer.dart';

pkgs/objective_c/lib/src/converter.dart

@@ -3,8 +3,11 @@
 // BSD-style license that can be found in the LICENSE file.
 
 import 'internal.dart';
+import 'ns_array.dart';
 import 'ns_date.dart';
+import 'ns_dictionary.dart';
 import 'ns_number.dart';
+import 'ns_set.dart';
 import 'ns_string.dart';
 import 'objective_c_bindings_generated.dart';
 
@@ -115,22 +118,39 @@ Object? toNullableDartObject(
 }
 
 extension NSArrayToDartList on NSArray {
+  /// Deep converts this [NSArray] to a Dart [List].
+  ///
+  /// This creates a new [List], converts all the [NSArray] elements, and adds
+  /// them to the [List]. If you only need iteration and element access,
+  /// [toDart] is much more efficient.
   List<Object> toDartList({
     Object Function(ObjCObjectBase) convertOther = _defaultDartConverter,
-  }) => map((o) => toDartObject(o, convertOther: convertOther)).toList();
+  }) =>
+      toDart().map((o) => toDartObject(o, convertOther: convertOther)).toList();
 }
 
 extension NSSetToDartSet on NSSet {
+  /// Deep converts this [NSSet] to a Dart [Set].
+  ///
+  /// This creates a new [Set], converts all the [NSSet] elements, and adds
+  /// them to the [Set]. If you only need iteration and element access,
+  /// [toDart] is much more efficient.
   Set<Object> toDartSet({
     Object Function(ObjCObjectBase) convertOther = _defaultDartConverter,
-  }) => map((o) => toDartObject(o, convertOther: convertOther)).toSet();
+  }) =>
+      toDart().map((o) => toDartObject(o, convertOther: convertOther)).toSet();
 }
 
 extension NSDictionaryToDartMap on NSDictionary {
+  /// Deep converts this [NSDictionary] to a Dart [Map].
+  ///
+  /// This creates a new [Map], converts all the [NSDictionary] elements, and
+  /// adds them to the [Map]. If you only need iteration and element access,
+  /// [toDart] is much more efficient.
   Map<Object, Object> toDartMap({
     Object Function(ObjCObjectBase) convertOther = _defaultDartConverter,
   }) => Map.fromEntries(
-    entries.map(
+    toDart().entries.map(
       (kv) => MapEntry(
         toDartObject(kv.key, convertOther: convertOther),
         toDartObject(kv.value, convertOther: convertOther),

pkgs/objective_c/lib/src/internal.dart

@@ -361,9 +361,9 @@ bool _isValidClass(ObjectPtr clazz, {bool forceReloadClasses = false}) {
 }
 
 /// Only for use by FFIgen bindings.
-class ObjCProtocolBase extends ObjCObjectBase {
-  ObjCProtocolBase(super.ptr, {required super.retain, required super.release});
-}
+// This exists so that interface_lists_test.dart can tell the difference between
+// a protocol and an interface.
+typedef ObjCProtocolBase = ObjCObjectBase;
 
 @pragma('vm:deeply-immutable')
 final class ObjCBlockRef extends _ObjCReference<c.ObjCBlockImpl> {

pkgs/objective_c/lib/src/ns_array.dart

@@ -0,0 +1,119 @@
+// Copyright (c) 2025, the Dart project authors. Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+import 'dart:collection';
+
+import 'converter.dart';
+import 'internal.dart';
+import 'objective_c_bindings_generated.dart';
+
+class _NSArrayAdapter with ListBase<ObjCObjectBase> {
+  final NSArray _array;
+
+  _NSArrayAdapter(this._array);
+
+  @override
+  int get length => _array.count;
+
+  @override
+  ObjCObjectBase elementAt(int index) => _array.objectAtIndex(index);
+
+  @override
+  Iterator<ObjCObjectBase> get iterator => _NSArrayIterator(this);
+
+  @override
+  ObjCObjectBase operator [](int index) => _array.objectAtIndex(index);
+
+  @override
+  set length(int newLength) => throw UnsupportedError('Cannot modify NSArray');
+
+  @override
+  void operator []=(int index, ObjCObjectBase value) =>
+      throw UnsupportedError('Cannot modify NSArray');
+
+  @override
+  void add(ObjCObjectBase value) =>
+      throw UnsupportedError('Cannot modify NSArray');
+}
+
+extension NSArrayToAdapter on NSArray {
+  /// Wraps this [NSArray] in an adapter that implements an immutable [List].
+  ///
+  /// This is not a conversion, doesn't create a new list, or change the
+  /// elements. For deep conversion, use [toDartList].
+  List<ObjCObjectBase> toDart() => _NSArrayAdapter(this);
+}
+
+class _NSMutableArrayAdapter with ListBase<ObjCObjectBase> {
+  final NSMutableArray _array;
+
+  _NSMutableArrayAdapter(this._array);
+
+  @override
+  int get length => _array.count;
+
+  @override
+  set length(int newLength) {
+    var len = length;
+    RangeError.checkValueInInterval(newLength, 0, len);
+    for (; len > newLength; --len) {
+      _array.removeLastObject();
+    }
+  }
+
+  @override
+  ObjCObjectBase elementAt(int index) => _array.objectAtIndex(index);
+
+  @override
+  Iterator<ObjCObjectBase> get iterator => _NSArrayIterator(this);
+
+  @override
+  ObjCObjectBase operator [](int index) => _array.objectAtIndex(index);
+
+  @override
+  void operator []=(int index, ObjCObjectBase value) =>
+      _array.replaceObjectAtIndex(index, withObject: value);
+
+  @override
+  void add(ObjCObjectBase value) => _array.addObject(value);
+}
+
+extension NSMutableArrayToAdapter on NSMutableArray {
+  /// Wraps this [NSMutableArray] in an adapter that implements [List].
+  ///
+  /// This is not a conversion, doesn't create a new list, or change the
+  /// elements. For deep conversion, use [toDartList].
+  List<ObjCObjectBase> toDart() => _NSMutableArrayAdapter(this);
+}
+
+class _NSArrayIterator implements Iterator<ObjCObjectBase> {
+  final Iterable<ObjCObjectBase> _iterable;
+  final int _length;
+  int _index;
+  ObjCObjectBase? _current;
+
+  _NSArrayIterator(Iterable<ObjCObjectBase> iterable)
+    : _iterable = iterable,
+      _length = iterable.length,
+      _index = 0;
+
+  @override
+  ObjCObjectBase get current => _current!;
+
+  @override
+  @pragma('vm:prefer-inline')
+  bool moveNext() {
+    final length = _iterable.length;
+    if (_length != length) {
+      throw ConcurrentModificationError(_iterable);
+    }
+    if (_index >= length) {
+      _current = null;
+      return false;
+    }
+    _current = _iterable.elementAt(_index);
+    _index++;
+    return true;
+  }
+}