[swift2objc] Typealias support (#2468)

liamappelbe · web-flow · commit ec69f12c5f72 · 2025-08-04T14:28:10.000+10:00
diff --git a/pkgs/swift2objc/lib/src/ast/_core/shared/referred_type.dart b/pkgs/swift2objc/lib/src/ast/_core/shared/referred_type.dart
@@ -3,6 +3,7 @@
 // BSD-style license that can be found in the LICENSE file.
 
 import '../../ast_node.dart';
+import '../../declarations/typealias_declaration.dart';
 import '../interfaces/declaration.dart';
 import '../interfaces/nestable_declaration.dart';
 import '../interfaces/objc_annotatable.dart';
@@ -15,14 +16,20 @@ sealed class ReferredType extends AstNode {
 
   abstract final String swiftType;
 
-  bool sameAs(ReferredType other);
+  bool _sameAs(ReferredType other);
 
   const ReferredType();
 
+  ReferredType get aliasedType;
+
   @override
   void visit(Visitation visitation) => visitation.visitReferredType(this);
 }
 
+extension ReferredTypeExt on ReferredType {
+  bool sameAs(ReferredType other) => aliasedType._sameAs(other.aliasedType);
+}
+
 /// Describes a reference of a declared type (user-defined or built-in).
 class DeclaredType<T extends Declaration> extends AstNode
     implements ReferredType {
@@ -39,15 +46,23 @@ class DeclaredType<T extends Declaration> extends AstNode
   final List<ReferredType> typeParams;
 
   @override
-  bool get isObjCRepresentable =>
-      declaration is ObjCAnnotatable &&
-      (declaration as ObjCAnnotatable).hasObjCAnnotation;
+  bool get isObjCRepresentable => switch (declaration) {
+        TypealiasDeclaration decl => decl.target.isObjCRepresentable,
+        ObjCAnnotatable decl => decl.hasObjCAnnotation,
+        _ => false,
+      };
 
   @override
   String get swiftType => name;
 
   @override
-  bool sameAs(ReferredType other) => other is DeclaredType && other.id == id;
+  bool _sameAs(ReferredType other) => other is DeclaredType && other.id == id;
+
+  @override
+  ReferredType get aliasedType => switch (declaration) {
+        TypealiasDeclaration decl => decl.target.aliasedType,
+        _ => this,
+      };
 
   const DeclaredType({
     required this.id,
@@ -83,7 +98,10 @@ class GenericType extends AstNode implements ReferredType {
   String get swiftType => name;
 
   @override
-  bool sameAs(ReferredType other) => other is GenericType && other.id == id;
+  bool _sameAs(ReferredType other) => other is GenericType && other.id == id;
+
+  @override
+  ReferredType get aliasedType => this;
 
   const GenericType({
     required this.id,
@@ -108,9 +126,12 @@ class OptionalType extends AstNode implements ReferredType {
   String get swiftType => '$child?';
 
   @override
-  bool sameAs(ReferredType other) =>
+  bool _sameAs(ReferredType other) =>
       other is OptionalType && child.sameAs(other.child);
 
+  @override
+  ReferredType get aliasedType => OptionalType(child.aliasedType);
+
   OptionalType(this.child);
 
   @override
diff --git a/pkgs/swift2objc/lib/src/ast/declarations/typealias_declaration.dart b/pkgs/swift2objc/lib/src/ast/declarations/typealias_declaration.dart
@@ -0,0 +1,34 @@
+// 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 '../_core/interfaces/nestable_declaration.dart';
+import '../_core/shared/referred_type.dart';
+import '../ast_node.dart';
+
+/// Describes the declaration of a Swift class.
+class TypealiasDeclaration extends AstNode implements InnerNestableDeclaration {
+  @override
+  final String id;
+
+  @override
+  final String name;
+
+  final ReferredType target;
+
+  @override
+  OuterNestableDeclaration? nestingParent;
+
+  TypealiasDeclaration(
+      {required this.id, required this.name, required this.target});
+
+  @override
+  void visit(Visitation visitation) =>
+      visitation.visitTypealiasDeclaration(this);
+
+  @override
+  void visitChildren(Visitor visitor) {
+    super.visitChildren(visitor);
+    visitor.visit(target);
+  }
+}
diff --git a/pkgs/swift2objc/lib/src/ast/visitor.dart b/pkgs/swift2objc/lib/src/ast/visitor.dart
@@ -4,24 +4,25 @@
 
 import 'package:logging/logging.dart';
 
-import '../ast/_core/interfaces/compound_declaration.dart';
-import '../ast/_core/interfaces/declaration.dart';
-import '../ast/_core/interfaces/enum_declaration.dart';
-import '../ast/_core/interfaces/function_declaration.dart';
-import '../ast/_core/interfaces/variable_declaration.dart';
-import '../ast/_core/shared/referred_type.dart';
-import '../ast/ast_node.dart';
-import '../ast/declarations/built_in/built_in_declaration.dart';
-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/protocol_declaration.dart';
-import '../ast/declarations/compounds/struct_declaration.dart';
-import '../ast/declarations/enums/associated_value_enum_declaration.dart';
-import '../ast/declarations/enums/normal_enum_declaration.dart';
-import '../ast/declarations/enums/raw_value_enum_declaration.dart';
-import '../ast/declarations/globals/globals.dart';
+import '_core/interfaces/compound_declaration.dart';
+import '_core/interfaces/declaration.dart';
+import '_core/interfaces/enum_declaration.dart';
+import '_core/interfaces/function_declaration.dart';
+import '_core/interfaces/variable_declaration.dart';
+import '_core/shared/referred_type.dart';
+import 'ast_node.dart';
+import 'declarations/built_in/built_in_declaration.dart';
+import 'declarations/compounds/class_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/protocol_declaration.dart';
+import 'declarations/compounds/struct_declaration.dart';
+import 'declarations/enums/associated_value_enum_declaration.dart';
+import 'declarations/enums/normal_enum_declaration.dart';
+import 'declarations/enums/raw_value_enum_declaration.dart';
+import 'declarations/globals/globals.dart';
+import 'declarations/typealias_declaration.dart';
 
 final _logger = Logger('swift2objc.visitor');
 
@@ -114,6 +115,8 @@ abstract class Visitation {
       visitEnumDeclaration(node);
   void visitRawValueEnumDeclaration<T>(RawValueEnumDeclaration<T> node) =>
       visitEnumDeclaration(node);
+  void visitTypealiasDeclaration(TypealiasDeclaration node) =>
+      visitDeclaration(node);
 
   /// Default behavior for all visit methods.
   void visitAstNode(AstNode node) => node.visitChildren(visitor);
diff --git a/pkgs/swift2objc/lib/src/parser/parsers/declaration_parsers/parse_typealias_declaration.dart b/pkgs/swift2objc/lib/src/parser/parsers/declaration_parsers/parse_typealias_declaration.dart
@@ -0,0 +1,31 @@
+// 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 '../../../ast/declarations/typealias_declaration.dart';
+import '../../_core/json.dart';
+import '../../_core/parsed_symbolgraph.dart';
+import '../../_core/token_list.dart';
+import '../../_core/utils.dart';
+import '../parse_type.dart';
+
+TypealiasDeclaration? parseTypealiasDeclaration(
+    Json typealiasSymbolJson, ParsedSymbolgraph symbolgraph) {
+  final id = parseSymbolId(typealiasSymbolJson);
+  final name = parseSymbolName(typealiasSymbolJson);
+  final declarationFragments = typealiasSymbolJson['declarationFragments'];
+
+  final malformedException = Exception(
+    'Malformed typealias at ${declarationFragments.path}: '
+    '$declarationFragments',
+  );
+
+  final tokens = TokenList(declarationFragments);
+  final equals = tokens.indexWhere((tok) => matchFragment(tok, 'text', '='));
+  if (equals == -1) throw malformedException;
+
+  final (target, remaining) = parseType(symbolgraph, tokens.slice(equals + 1));
+  if (remaining.isNotEmpty) throw malformedException;
+
+  return TypealiasDeclaration(id: id, name: name, target: target);
+}
diff --git a/pkgs/swift2objc/lib/src/parser/parsers/parse_declarations.dart b/pkgs/swift2objc/lib/src/parser/parsers/parse_declarations.dart
@@ -10,6 +10,7 @@ import '../_core/utils.dart';
 import 'declaration_parsers/parse_compound_declaration.dart';
 import 'declaration_parsers/parse_function_declaration.dart';
 import 'declaration_parsers/parse_initializer_declaration.dart';
+import 'declaration_parsers/parse_typealias_declaration.dart';
 import 'declaration_parsers/parse_variable_declaration.dart';
 
 List<Declaration> parseDeclarations(ParsedSymbolgraph symbolgraph) {
@@ -56,6 +57,7 @@ Declaration parseDeclaration(
     'swift.init' => parseInitializerDeclaration(symbolJson, symbolgraph),
     'swift.func' => parseGlobalFunctionDeclaration(symbolJson, symbolgraph),
     'swift.var' => parseGlobalVariableDeclaration(symbolJson, symbolgraph),
+    'swift.typealias' => parseTypealiasDeclaration(symbolJson, symbolgraph),
     _ => throw Exception(
         'Symbol of type $symbolType is not implemented yet.',
       ),
diff --git a/pkgs/swift2objc/lib/src/transformer/_core/utils.dart b/pkgs/swift2objc/lib/src/transformer/_core/utils.dart
@@ -8,6 +8,7 @@ import '../../ast/_core/shared/referred_type.dart';
 import '../../ast/declarations/compounds/class_declaration.dart';
 import '../../ast/declarations/compounds/members/initializer_declaration.dart';
 import '../../ast/declarations/compounds/members/property_declaration.dart';
+import '../../ast/declarations/typealias_declaration.dart';
 import '../../transformer/_core/primitive_wrappers.dart';
 import '../transform.dart';
 import 'unique_namer.dart';
@@ -35,8 +36,15 @@ import 'unique_namer.dart';
   if (type is GenericType) {
     throw UnimplementedError('Generic types are not implemented yet');
   } else if (type is DeclaredType) {
+    final declaration = type.declaration;
+    if (declaration is TypealiasDeclaration) {
+      return maybeWrapValue(
+          declaration.target, value, globalNamer, transformationMap,
+          shouldWrapPrimitives: shouldWrapPrimitives);
+    }
+
     final transformedTypeDeclaration = transformDeclaration(
-      type.declaration,
+      declaration,
       globalNamer,
       transformationMap,
     );
@@ -72,6 +80,8 @@ import 'unique_namer.dart';
     if (declaration is ClassDeclaration) {
       final wrappedInstance = declaration.wrappedInstance!;
       return ('$value.${wrappedInstance.name}', wrappedInstance.type);
+    } else if (declaration is TypealiasDeclaration) {
+      return maybeUnwrapValue(declaration.target, value);
     } else {
       return (value, type);
     }
diff --git a/pkgs/swift2objc/lib/src/transformer/transform.dart b/pkgs/swift2objc/lib/src/transformer/transform.dart
@@ -9,21 +9,22 @@ import '../ast/declarations/built_in/built_in_declaration.dart';
 import '../ast/declarations/compounds/class_declaration.dart';
 import '../ast/declarations/compounds/struct_declaration.dart';
 import '../ast/declarations/globals/globals.dart';
+import '../ast/declarations/typealias_declaration.dart';
 import '../ast/visitor.dart';
 import '_core/dependencies.dart';
 import '_core/unique_namer.dart';
 import 'transformers/transform_compound.dart';
 import 'transformers/transform_globals.dart';
 
-typedef TransformationMap = Map<Declaration, Declaration>;
+typedef TransformationMap = Map<Declaration, Declaration?>;
 
 Set<Declaration> generateDependencies(Iterable<Declaration> decls) =>
     visit(DependencyVisitation(), decls).topLevelDeclarations;
 
 /// Transforms the given declarations into the desired ObjC wrapped declarations
 List<Declaration> transform(List<Declaration> declarations,
     {required bool Function(Declaration) filter}) {
-  final transformationMap = <Declaration, Declaration>{};
+  final transformationMap = <Declaration, Declaration?>{};
 
   final declarations0 = declarations.where(filter).toSet();
   declarations0.addAll(generateDependencies(declarations0));
@@ -45,9 +46,11 @@ List<Declaration> transform(List<Declaration> declarations,
       .toList();
 
   final transformedDeclarations = [
-    ...nonGlobals.map(
-      (decl) => transformDeclaration(decl, globalNamer, transformationMap),
-    ),
+    ...nonGlobals
+        .map(
+          (d) => maybeTransformDeclaration(d, globalNamer, transformationMap),
+        )
+        .nonNulls,
     if (globals.functions.isNotEmpty || globals.variables.isNotEmpty)
       transformGlobals(globals, globalNamer, transformationMap),
   ];
@@ -62,9 +65,19 @@ Declaration transformDeclaration(
   UniqueNamer parentNamer,
   TransformationMap transformationMap, {
   bool nested = false,
+}) =>
+    maybeTransformDeclaration(declaration, parentNamer, transformationMap,
+        nested: nested) ??
+    declaration;
+
+Declaration? maybeTransformDeclaration(
+  Declaration declaration,
+  UniqueNamer parentNamer,
+  TransformationMap transformationMap, {
+  bool nested = false,
 }) {
-  if (transformationMap[declaration] != null) {
-    return transformationMap[declaration]!;
+  if (transformationMap.containsKey(declaration)) {
+    return transformationMap[declaration];
   }
 
   if (declaration is InnerNestableDeclaration &&
@@ -80,6 +93,7 @@ Declaration transformDeclaration(
         parentNamer,
         transformationMap,
       ),
+    TypealiasDeclaration() => null,
     _ => throw UnimplementedError(),
   };
 }
@@ -89,5 +103,6 @@ List<Declaration> _getPrimitiveWrapperClasses(
   return transformationMap.entries
       .where((entry) => entry.key is BuiltInDeclaration)
       .map((entry) => entry.value)
+      .nonNulls
       .toList();
 }
diff --git a/pkgs/swift2objc/lib/src/transformer/transformers/transform_compound.dart b/pkgs/swift2objc/lib/src/transformer/transformers/transform_compound.dart
@@ -44,9 +44,10 @@ ClassDeclaration transformCompound(
   transformationMap[originalCompound] = transformedCompound;
 
   transformedCompound.nestedDeclarations = originalCompound.nestedDeclarations
-      .map((nested) => transformDeclaration(
+      .map((nested) => maybeTransformDeclaration(
               nested, compoundNamer, transformationMap, nested: true)
-          as InnerNestableDeclaration)
+          as InnerNestableDeclaration?)
+      .nonNulls
       .toList()
     ..sort((Declaration a, Declaration b) => a.id.compareTo(b.id));
   transformedCompound.nestedDeclarations
diff --git a/pkgs/swift2objc/lib/src/transformer/transformers/transform_referred_type.dart b/pkgs/swift2objc/lib/src/transformer/transformers/transform_referred_type.dart
@@ -4,6 +4,7 @@
 
 import '../../ast/_core/interfaces/declaration.dart';
 import '../../ast/_core/shared/referred_type.dart';
+import '../../ast/declarations/typealias_declaration.dart';
 import '../_core/unique_namer.dart';
 import '../transform.dart';
 
@@ -20,8 +21,12 @@ ReferredType transformReferredType(
   if (type is GenericType) {
     throw UnimplementedError('Generic types are not supported yet');
   } else if (type is DeclaredType) {
+    final decl = type.declaration;
+    if (decl is TypealiasDeclaration) {
+      return transformReferredType(decl.target, globalNamer, transformationMap);
+    }
     return transformDeclaration(
-      type.declaration,
+      decl,
       globalNamer,
       transformationMap,
     ).asDeclaredType;
diff --git a/pkgs/swift2objc/lib/src/transformer/transformers/transform_variable.dart b/pkgs/swift2objc/lib/src/transformer/transformers/transform_variable.dart
@@ -1,5 +1,6 @@
 import '../../ast/_core/interfaces/declaration.dart';
 import '../../ast/_core/interfaces/variable_declaration.dart';
+import '../../ast/_core/shared/referred_type.dart';
 import '../../ast/declarations/compounds/members/method_declaration.dart';
 import '../../ast/declarations/compounds/members/property_declaration.dart';
 import '../../ast/declarations/globals/globals.dart';
diff --git a/pkgs/swift2objc/test/integration/typealias_input.swift b/pkgs/swift2objc/test/integration/typealias_input.swift
@@ -0,0 +1,14 @@
+public typealias Foo = Int;
+public typealias FooFoo = Foo;
+public typealias Bar = MyClass;
+public typealias BarBar = Bar;
+public typealias BarNullable = Bar?;
+
+public class MyClass {
+  public typealias Baz = Bar;
+
+  public func method1(x: Foo) -> FooFoo { return 123; }
+  public func method2(x: Bar) -> BarBar { return x; }
+  public func method3(x: BarNullable) -> BarNullable { return x; }
+  public func method4(x: Baz) -> Baz { return x; }
+}
diff --git a/pkgs/swift2objc/test/integration/typealias_output.swift b/pkgs/swift2objc/test/integration/typealias_output.swift
