[swift2objc] Support wrapper classes for primitives (#1984)

pkgs/swift2objc/lib/src/transformer/_core/primitive_wrappers.dart

@@ -0,0 +1,65 @@
+// 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 'package:collection/collection.dart';
+
+import '../../ast/_core/interfaces/declaration.dart';
+import '../../ast/_core/shared/referred_type.dart';
+import '../../ast/declarations/built_in/built_in_declaration.dart';
+import '../../ast/declarations/compounds/class_declaration.dart';
+import '../../ast/declarations/compounds/members/property_declaration.dart';
+import '../../parser/_core/utils.dart';
+import '../../transformer/_core/utils.dart';
+import '../transform.dart';
+
+final _primitiveWrappers = List<(ReferredType, ReferredType)>.unmodifiable([
+  (intType, _createWrapperClass(intType)),
+  (floatType, _createWrapperClass(floatType)),
+  (doubleType, _createWrapperClass(doubleType)),
+  (boolType, _createWrapperClass(boolType)),
+]);
+
+ReferredType _createWrapperClass(DeclaredType primitiveType) {
+  final property = PropertyDeclaration(
+    id: primitiveType.id.addIdSuffix('wrappedInstance'),
+    name: 'wrappedInstance',
+    type: primitiveType,
+  );
+  return ClassDeclaration(
+          id: primitiveType.id.addIdSuffix('wrapper'),
+          name: '${primitiveType.name}Wrapper',
+          hasObjCAnnotation: true,
+          superClass: objectType,
+          isWrapper: true,
+          wrappedInstance: property,
+          wrapperInitializer: buildWrapperInitializer(property))
+      .asDeclaredType;
+}
+
+// Support Optional primitives as return Type
+// TODO(https://github.com/dart-lang/native/issues/1743)
+
+(ReferredType, bool) maybeGetPrimitiveWrapper(
+  ReferredType type,
+  bool shouldWrapPrimitives,
+  TransformationMap transformationMap,
+) {
+  if (type is! DeclaredType || !shouldWrapPrimitives) {
+    return (type, false);
+  }
+
+  final wrapper = _getPrimitiveWrapper(type);
+  if (wrapper == null) {
+    return (type, false);
+  }
+
+  transformationMap[type.declaration] = (wrapper as DeclaredType).declaration;
+  return (wrapper, true);
+}
+
+ReferredType? _getPrimitiveWrapper(DeclaredType other) {
+  return _primitiveWrappers
+      .firstWhereOrNull((pair) => pair.$1.sameAs(other))
+      ?.$2;
+}

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

@@ -3,21 +3,31 @@
 // BSD-style license that can be found in the LICENSE file.
 
 import '../../ast/_core/interfaces/declaration.dart';
+import '../../ast/_core/shared/parameter.dart';
 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 '../../transformer/_core/primitive_wrappers.dart';
 import '../transform.dart';
 import 'unique_namer.dart';
 
 // TODO(https://github.com/dart-lang/native/issues/1358): These functions should
 // probably be methods on ReferredType, but the transformDeclaration call makes
 // that weird. Refactor this as part of the transformer refactor.
 
-(String value, ReferredType type) maybeWrapValue(
-  ReferredType type,
-  String value,
-  UniqueNamer globalNamer,
-  TransformationMap transformationMap,
-) {
+(String value, ReferredType type) maybeWrapValue(ReferredType type,
+    String value, UniqueNamer globalNamer, TransformationMap transformationMap,
+    {bool shouldWrapPrimitives = false}) {
+  final (wrappedPrimitiveType, returnsWrappedPrimitive) =
+      maybeGetPrimitiveWrapper(type, shouldWrapPrimitives, transformationMap);
+  if (returnsWrappedPrimitive) {
+    return (
+      '${(wrappedPrimitiveType as DeclaredType).name}($value)',
+      wrappedPrimitiveType
+    );
+  }
+
   if (type.isObjCRepresentable) {
     return (value, type);
   }
@@ -77,3 +87,24 @@ import 'unique_namer.dart';
     throw UnimplementedError('Unknown type: $type');
   }
 }
+
+InitializerDeclaration buildWrapperInitializer(
+  PropertyDeclaration wrappedClassInstance,
+) {
+  return InitializerDeclaration(
+    id: '',
+    params: [
+      Parameter(
+        name: '_',
+        internalName: 'wrappedInstance',
+        type: wrappedClassInstance.type,
+      )
+    ],
+    isOverriding: false,
+    isFailable: false,
+    throws: false,
+    async: false,
+    statements: ['self.${wrappedClassInstance.name} = wrappedInstance'],
+    hasObjCAnnotation: wrappedClassInstance.hasObjCAnnotation,
+  );
+}

pkgs/swift2objc/lib/src/transformer/transform.dart

@@ -5,6 +5,7 @@
 import '../ast/_core/interfaces/compound_declaration.dart';
 import '../ast/_core/interfaces/declaration.dart';
 import '../ast/_core/interfaces/nestable_declaration.dart';
+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';
@@ -51,7 +52,8 @@ List<Declaration> transform(List<Declaration> declarations,
       transformGlobals(globals, globalNamer, transformationMap),
   ];
 
-  return transformedDeclarations
+  return (transformedDeclarations +
+      _getPrimitiveWrapperClasses(transformationMap))
     ..sort((Declaration a, Declaration b) => a.id.compareTo(b.id));
 }
 
@@ -80,3 +82,11 @@ Declaration transformDeclaration(
     _ => throw UnimplementedError(),
   };
 }
+
+List<Declaration> _getPrimitiveWrapperClasses(
+    TransformationMap transformationMap) {
+  return transformationMap.entries
+      .where((entry) => entry.key is BuiltInDeclaration)
+      .map((entry) => entry.value)
+      .toList();
+}

pkgs/swift2objc/lib/src/transformer/transformers/transform_compound.dart

@@ -5,14 +5,14 @@
 import '../../ast/_core/interfaces/compound_declaration.dart';
 import '../../ast/_core/interfaces/declaration.dart';
 import '../../ast/_core/interfaces/nestable_declaration.dart';
-import '../../ast/_core/shared/parameter.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 '../../parser/_core/utils.dart';
 import '../_core/unique_namer.dart';
+import '../_core/utils.dart';
 import '../transform.dart';
 import 'transform_function.dart';
 import 'transform_initializer.dart';
@@ -38,7 +38,7 @@ ClassDeclaration transformCompound(
     superClass: objectType,
     isWrapper: true,
     wrappedInstance: wrappedCompoundInstance,
-    wrapperInitializer: _buildWrapperInitializer(wrappedCompoundInstance),
+    wrapperInitializer: buildWrapperInitializer(wrappedCompoundInstance),
   );
 
   transformationMap[originalCompound] = transformedCompound;
@@ -98,24 +98,3 @@ ClassDeclaration transformCompound(
 
   return transformedCompound;
 }
-
-InitializerDeclaration _buildWrapperInitializer(
-  PropertyDeclaration wrappedClassInstance,
-) {
-  return InitializerDeclaration(
-    id: '',
-    params: [
-      Parameter(
-        name: '_',
-        internalName: 'wrappedInstance',
-        type: wrappedClassInstance.type,
-      )
-    ],
-    isOverriding: false,
-    isFailable: false,
-    throws: false,
-    async: false,
-    statements: ['self.${wrappedClassInstance.name} = wrappedInstance'],
-    hasObjCAnnotation: wrappedClassInstance.hasObjCAnnotation,
-  );
-}

pkgs/swift2objc/lib/src/transformer/transformers/transform_function.dart

@@ -84,16 +84,17 @@ MethodDeclaration _transformFunction(
       )
       .toList();
 
-  final transformedReturnType = transformReferredType(
-    originalFunction.returnType,
-    globalNamer,
-    transformationMap,
-  );
+  final localNamer = UniqueNamer();
+  final resultName = localNamer.makeUnique('result');
+
+  final (wrapperResult, type) = maybeWrapValue(
+      originalFunction.returnType, resultName, globalNamer, transformationMap,
+      shouldWrapPrimitives: originalFunction.throws);
 
   final transformedMethod = MethodDeclaration(
     id: originalFunction.id,
     name: wrapperMethodName,
-    returnType: transformedReturnType,
+    returnType: type,
     params: transformedParams,
     hasObjCAnnotation: true,
     isStatic: originalFunction is MethodDeclaration
@@ -107,6 +108,9 @@ MethodDeclaration _transformFunction(
     originalFunction,
     transformedMethod,
     globalNamer,
+    localNamer,
+    resultName,
+    wrapperResult,
     transformationMap,
     originalCallGenerator: originalCallStatementGenerator,
   );
@@ -144,10 +148,12 @@ List<String> _generateStatements(
   FunctionDeclaration originalFunction,
   MethodDeclaration transformedMethod,
   UniqueNamer globalNamer,
+  UniqueNamer localNamer,
+  String resultName,
+  String wrappedResult,
   TransformationMap transformationMap, {
   required String Function(String arguments) originalCallGenerator,
 }) {
-  final localNamer = UniqueNamer();
   final arguments = generateInvocationParams(
       localNamer, originalFunction.params, transformedMethod.params);
   var originalMethodCall = originalCallGenerator(arguments);
@@ -166,22 +172,8 @@ List<String> _generateStatements(
     throw UnimplementedError('Generic types are not implemented yet');
   }
 
-  final resultName = localNamer.makeUnique('result');
-  final methodCallStmt = 'let $resultName = $originalMethodCall';
-
-  final (wrappedResult, wrapperType) = maybeWrapValue(
-    originalFunction.returnType,
-    resultName,
-    globalNamer,
-    transformationMap,
-  );
-
-  assert(wrapperType.sameAs(transformedMethod.returnType));
-
-  final returnStmt = 'return $wrappedResult';
-
   return [
-    methodCallStmt,
-    returnStmt,
+    'let $resultName = $originalMethodCall',
+    'return $wrappedResult',
   ];
 }

pkgs/swift2objc/lib/src/transformer/transformers/transform_variable.dart

@@ -73,24 +73,32 @@ Declaration _transformVariable(
       ? originalVariable.hasSetter
       : !originalVariable.isConstant;
 
+  // properties that throw or are async need to be wrapped in a method
   if (originalVariable.throws || originalVariable.async) {
     final prefix = [
       if (originalVariable.throws) 'try',
       if (originalVariable.async) 'await'
     ].join(' ');
 
+    final localNamer = UniqueNamer();
+    final resultName = localNamer.makeUnique('result');
+
+    final (wrapperResult, type) = maybeWrapValue(
+        originalVariable.type, resultName, globalNamer, transformationMap,
+        shouldWrapPrimitives: originalVariable.throws);
+
     return MethodDeclaration(
       id: originalVariable.id,
       name: wrapperPropertyName,
-      returnType: transformedType,
+      returnType: type,
       params: [],
       hasObjCAnnotation: true,
       isStatic: originalVariable is PropertyDeclaration
           ? originalVariable.isStatic
           : true,
       statements: [
-        'let result = $prefix $variableReferenceExpression',
-        'return $transformedType(result)',
+        'let $resultName = $prefix $variableReferenceExpression',
+        'return $wrapperResult',
       ],
       throws: originalVariable.throws,
       async: originalVariable.async,

pkgs/swift2objc/pubspec.yaml

@@ -15,6 +15,7 @@ topics:
   - codegen
 
 dependencies:
+  collection: ^1.19.1
   logging: ^1.3.0
   meta: ^1.16.0
   path: ^1.9.0