WIP: [swift2objc] Subscript support

pkgs/swift2objc/CHANGELOG.md

@@ -2,6 +2,9 @@
 
 - Added support for inout parameters. Preserve inout types in AST and generate
   correct & pass-by-reference invocation syntax.
+- Added support for Swift subscripts. Non-representable subscripts (static, 
+  throwing, async, or with multiple/optional parameters) are automatically
+  transformed into `@objc` methods.
 
 ## 0.1.0
 

pkgs/swift2objc/lib/src/ast/_core/interfaces/compound_declaration.dart

@@ -5,6 +5,7 @@
 import '../../declarations/compounds/members/initializer_declaration.dart';
 import '../../declarations/compounds/members/method_declaration.dart';
 import '../../declarations/compounds/members/property_declaration.dart';
+import '../../declarations/compounds/members/subscript_declaration.dart';
 import 'declaration.dart';
 import 'nestable_declaration.dart';
 import 'protocol_conformable.dart';
@@ -22,5 +23,6 @@ abstract interface class CompoundDeclaration
         InnerNestableDeclaration {
   abstract List<PropertyDeclaration> properties;
   abstract List<MethodDeclaration> methods;
+  abstract List<SubscriptDeclaration> subscripts;
   abstract List<InitializerDeclaration> initializers;
 }

pkgs/swift2objc/lib/src/ast/declarations/compounds/class_declaration.dart

@@ -14,6 +14,7 @@ import '../built_in/built_in_declaration.dart';
 import 'members/initializer_declaration.dart';
 import 'members/method_declaration.dart';
 import 'members/property_declaration.dart';
+import 'members/subscript_declaration.dart';
 import 'protocol_declaration.dart';
 
 /// Describes the declaration of a Swift class.
@@ -40,6 +41,9 @@ class ClassDeclaration extends AstNode
   @override
   List<MethodDeclaration> methods;
 
+  @override
+  List<SubscriptDeclaration> subscripts;
+
   @override
   List<DeclaredType<ProtocolDeclaration>> conformedProtocols;
 
@@ -82,6 +86,7 @@ class ClassDeclaration extends AstNode
     this.lineNumber,
     this.properties = const [],
     this.methods = const [],
+    this.subscripts = const [],
     this.nestingParent,
     this.nestedDeclarations = const [],
     this.conformedProtocols = const [],
@@ -107,6 +112,7 @@ class ClassDeclaration extends AstNode
     super.visitChildren(visitor);
     visitor.visitAll(properties);
     visitor.visitAll(methods);
+    visitor.visitAll(subscripts);
     visitor.visitAll(conformedProtocols);
     visitor.visitAll(typeParams);
     visitor.visit(superClass);

pkgs/swift2objc/lib/src/ast/declarations/compounds/enum_declaration.dart

@@ -14,6 +14,7 @@ import '../../ast_node.dart';
 import 'members/initializer_declaration.dart';
 import 'members/method_declaration.dart';
 import 'members/property_declaration.dart';
+import 'members/subscript_declaration.dart';
 import 'protocol_declaration.dart';
 
 /// Describes the declaration of a Swift enum.
@@ -41,6 +42,9 @@ class EnumDeclaration extends AstNode implements CompoundDeclaration {
   @override
   List<MethodDeclaration> methods;
 
+  @override
+  List<SubscriptDeclaration> subscripts;
+
   @override
   List<InitializerDeclaration> initializers;
 
@@ -65,6 +69,7 @@ class EnumDeclaration extends AstNode implements CompoundDeclaration {
     required this.cases,
     required this.properties,
     required this.methods,
+    this.subscripts = const [],
     required this.initializers,
     this.conformedProtocols = const [],
     this.typeParams = const [],
@@ -81,6 +86,7 @@ class EnumDeclaration extends AstNode implements CompoundDeclaration {
     visitor.visitAll(cases);
     visitor.visitAll(properties);
     visitor.visitAll(methods);
+    visitor.visitAll(subscripts);
     visitor.visitAll(initializers);
     visitor.visitAll(typeParams);
     visitor.visitAll(conformedProtocols);

pkgs/swift2objc/lib/src/ast/declarations/compounds/members/subscript_declaration.dart

@@ -0,0 +1,83 @@
+// Copyright (c) 2024, the Dart project authors. Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+import '../../../../config.dart';
+import '../../../_core/interfaces/availability.dart';
+import '../../../_core/interfaces/can_async.dart';
+import '../../../_core/interfaces/can_throw.dart';
+import '../../../_core/interfaces/declaration.dart';
+import '../../../_core/interfaces/objc_annotatable.dart';
+import '../../../_core/shared/parameter.dart';
+import '../../../_core/shared/referred_type.dart';
+import '../../../ast_node.dart';
+import 'property_declaration.dart';
+
+/// Describes a subscript declaration for a Swift compound entity
+class SubscriptDeclaration extends AstNode
+    implements Declaration, ObjCAnnotatable, CanThrow, CanAsync {
+  @override
+  String id;
+
+  @override
+  String name = 'subscript';
+
+  @override
+  InputConfig? source;
+
+  @override
+  final int? lineNumber;
+
+  @override
+  List<AvailabilityInfo> availability;
+
+  @override
+  bool hasObjCAnnotation;
+
+  ReferredType returnType;
+
+  List<Parameter> params;
+
+  @override
+  bool throws;
+
+  @override
+  bool async;
+
+  bool mutating;
+
+  bool hasSetter;
+
+  PropertyStatements? getter;
+  PropertyStatements? setter;
+
+  bool isStatic;
+
+  SubscriptDeclaration({
+    required this.id,
+    required this.source,
+    required this.availability,
+    required this.returnType,
+    required this.params,
+    this.lineNumber,
+    this.hasSetter = false,
+    this.hasObjCAnnotation = false,
+    this.getter,
+    this.setter,
+    this.isStatic = false,
+    this.throws = false,
+    this.async = false,
+    this.mutating = false,
+  });
+
+  @override
+  void visit(Visitation visitation) =>
+      visitation.visitSubscriptDeclaration(this);
+
+  @override
+  void visitChildren(Visitor visitor) {
+    super.visitChildren(visitor);
+    visitor.visitAll(params);
+    visitor.visit(returnType);
+  }
+}

pkgs/swift2objc/lib/src/ast/declarations/compounds/protocol_declaration.dart

@@ -11,6 +11,7 @@ import '../../ast_node.dart';
 import 'members/initializer_declaration.dart';
 import 'members/method_declaration.dart';
 import 'members/property_declaration.dart';
+import 'members/subscript_declaration.dart';
 
 /// Describes the declaration of a Swift protocol.
 class ProtocolDeclaration extends AstNode implements CompoundDeclaration {
@@ -35,6 +36,9 @@ class ProtocolDeclaration extends AstNode implements CompoundDeclaration {
   @override
   List<MethodDeclaration> methods;
 
+  @override
+  List<SubscriptDeclaration> subscripts;
+
   @override
   List<DeclaredType<ProtocolDeclaration>> conformedProtocols;
 
@@ -58,6 +62,7 @@ class ProtocolDeclaration extends AstNode implements CompoundDeclaration {
     required this.availability,
     required this.properties,
     required this.methods,
+    required this.subscripts,
     required this.initializers,
     required this.conformedProtocols,
     required this.typeParams,
@@ -73,7 +78,9 @@ class ProtocolDeclaration extends AstNode implements CompoundDeclaration {
   void visitChildren(Visitor visitor) {
     super.visitChildren(visitor);
     visitor.visitAll(properties);
+    visitor.visitAll(properties);
     visitor.visitAll(methods);
+    visitor.visitAll(subscripts);
     visitor.visitAll(conformedProtocols);
     visitor.visitAll(typeParams);
     visitor.visitAll(initializers);

pkgs/swift2objc/lib/src/ast/declarations/compounds/struct_declaration.dart

@@ -11,6 +11,7 @@ import '../../ast_node.dart';
 import 'members/initializer_declaration.dart';
 import 'members/method_declaration.dart';
 import 'members/property_declaration.dart';
+import 'members/subscript_declaration.dart';
 import 'protocol_declaration.dart';
 
 /// Describes the declaration of a Swift struct.
@@ -36,6 +37,9 @@ class StructDeclaration extends AstNode implements CompoundDeclaration {
   @override
   List<MethodDeclaration> methods;
 
+  @override
+  List<SubscriptDeclaration> subscripts;
+
   @override
   List<DeclaredType<ProtocolDeclaration>> conformedProtocols;
 
@@ -59,6 +63,7 @@ class StructDeclaration extends AstNode implements CompoundDeclaration {
     required this.availability,
     this.properties = const [],
     this.methods = const [],
+    this.subscripts = const [],
     this.initializers = const [],
     this.conformedProtocols = const [],
     this.typeParams = const [],
@@ -73,7 +78,9 @@ class StructDeclaration extends AstNode implements CompoundDeclaration {
   void visitChildren(Visitor visitor) {
     super.visitChildren(visitor);
     visitor.visitAll(properties);
+    visitor.visitAll(properties);
     visitor.visitAll(methods);
+    visitor.visitAll(subscripts);
     visitor.visitAll(conformedProtocols);
     visitor.visitAll(typeParams);
     visitor.visitAll(initializers);

pkgs/swift2objc/lib/src/ast/visitor.dart

@@ -15,6 +15,7 @@ import 'declarations/compounds/enum_declaration.dart';
 import 'declarations/compounds/members/initializer_declaration.dart';
 import 'declarations/compounds/members/method_declaration.dart';
 import 'declarations/compounds/members/property_declaration.dart';
+import 'declarations/compounds/members/subscript_declaration.dart';
 import 'declarations/compounds/protocol_declaration.dart';
 import 'declarations/compounds/struct_declaration.dart';
 import 'declarations/globals/globals.dart';
@@ -96,6 +97,8 @@ abstract class Visitation {
       visitVariableDeclaration(node);
   void visitGlobalVariableDeclaration(GlobalVariableDeclaration node) =>
       visitVariableDeclaration(node);
+  void visitSubscriptDeclaration(SubscriptDeclaration node) =>
+      visitDeclaration(node);
   void visitCompoundDeclaration(CompoundDeclaration node) =>
       visitDeclaration(node);
   void visitClassDeclaration(ClassDeclaration node) =>

pkgs/swift2objc/lib/src/generator/generators/class_generator.dart

@@ -8,6 +8,7 @@ import '../../ast/declarations/compounds/class_declaration.dart';
 import '../../ast/declarations/compounds/members/initializer_declaration.dart';
 import '../../ast/declarations/compounds/members/method_declaration.dart';
 import '../../ast/declarations/compounds/members/property_declaration.dart';
+import '../../ast/declarations/compounds/members/subscript_declaration.dart';
 import '../_core/utils.dart';
 import '../generator.dart';
 
@@ -19,6 +20,7 @@ List<String> generateClass(ClassDeclaration declaration) {
     ...[
       _generateClassWrappedInstance(declaration),
       ..._generateClassProperties(declaration),
+      ..._generateClassSubscripts(declaration),
       ..._generateInitializers(declaration),
       ..._generateClassMethods(declaration),
       ..._generateNestedDeclarations(declaration),
@@ -144,6 +146,48 @@ List<String> _generateClassProperties(ClassDeclaration declaration) => [
     ..._generateClassProperty(property),
 ];
 
+List<String> _generateClassSubscripts(ClassDeclaration declaration) => [
+  for (final subscript in declaration.subscripts)
+    ..._generateClassSubscript(subscript),
+];
+
+List<String> _generateClassSubscript(SubscriptDeclaration subscript) {
+  final header = StringBuffer();
+
+  if (subscript.hasObjCAnnotation) {
+    header.write('@objc ');
+  }
+
+  if (subscript.isStatic) {
+    header.write('static ');
+  }
+
+  final params = generateParameters(subscript.params);
+  header.write(
+    'public subscript($params) -> ${subscript.returnType.swiftType} {',
+  );
+
+  final getterLines = [
+    'get ${generateAnnotations(subscript)}{',
+    ...(subscript.getter?.statements.indent() ?? <String>[]),
+    '}',
+  ];
+
+  final setterLines = [
+    'set {',
+    ...(subscript.setter?.statements.indent() ?? <String>[]),
+    '}',
+  ];
+
+  return [
+    ...generateAvailability(subscript),
+    header.toString(),
+    ...getterLines.indent(),
+    if (subscript.hasSetter) ...setterLines.indent(),
+    '}\n',
+  ];
+}
+
 List<String> _generateClassProperty(PropertyDeclaration property) {
   final header = StringBuffer();
 

pkgs/swift2objc/lib/src/parser/_core/token_list.dart

@@ -32,7 +32,7 @@ class TokenList extends Iterable<Json> {
 
   @visibleForTesting
   static Iterable<Json> splitToken(Json token) sync* {
-    const splittables = ['(', ')', '?', ',', '->'];
+    const splittables = ['(', ')', '?', ',', '->', '[', ']', ':'];
     Json textToken(String text) =>
         Json({'kind': 'text', 'spelling': text}, token.pathSegments);
 

pkgs/swift2objc/lib/src/parser/_core/utils.dart

@@ -82,8 +82,12 @@ bool parseSymbolHasObjcAnnotation(Json symbolJson) =>
       (json) => matchFragment(json, 'attribute', '@objc'),
     );
 
-bool parseIsOverriding(Json symbolJson) => symbolJson['declarationFragments']
-    .any((json) => matchFragment(json, 'keyword', 'override'));
+bool parseIsOverriding(Json symbolJson) =>
+    findKeywordInFragments(symbolJson['declarationFragments'], 'override');
+
+bool findKeywordInFragments(Json json, String keyword) {
+  return json.any((frag) => matchFragment(frag, 'keyword', keyword));
+}
 
 List<AvailabilityInfo> parseAvailability(Json symbolJson) {
   final availability = symbolJson['availability'];
@@ -165,3 +169,14 @@ ReferredType parseTypeAfterSeparator(
   assert(suffix.isEmpty, '$suffix');
   return type;
 }
+
+ReferredType parseReturnType(
+  Context context,
+  Json symbolJson,
+  ParsedSymbolgraph symbolgraph,
+) {
+  final returnJson = TokenList(symbolJson['functionSignature']['returns']);
+  final (returnType, unparsed) = parseType(context, symbolgraph, returnJson);
+  assert(unparsed.isEmpty, '$returnJson\n\n$returnType\n\n$unparsed\n');
+  return returnType;
+}