Macro: Macros Add `abstract` keyword To Sealed Type Augmentations Which Breaks Code

[mcmah309]

For the code

final variantRegex = RegExp(r'^(\w+)\((.*?)\)$');

macro class Enum
    implements ClassTypesMacro, ClassDeclarationsMacro, ClassDefinitionMacro {


      final String? variant1, variant2;

  const Enum([this.variant1, this.variant2]);

  List<String> get variants => [
    if(variant1 != null) variant1!,
    if(variant2 != null) variant2!
    ];

  @override
  FutureOr<void> buildTypesForClass(ClassDeclaration clazz, ClassTypeBuilder builder) {
    final className = clazz.identifier.name;
    for(final variant in variants) {
      final match = variantRegex.firstMatch(variant);
      if (match == null) {
        throw Exception("Variant `$variant` is not valid");
      }
      final newTypeName = match.group(1)!;
      final fieldTypes = match.group(2)!.split(',').map((s) => s.trim()).toList();
      int count = 1;
      final fields = StringBuffer();
      final constructors = StringBuffer();
      for(final fieldType in fieldTypes) {
        fields.write("\t$fieldType v$count;\n");
        constructors.write("this.v$count,");
      }
      builder.declareType(newTypeName, DeclarationCode.fromString('''
final class $className\$$newTypeName implements $className {
$fields

  $className\$$newTypeName._($constructors);
}'''));
    }
  }

  @override
  Future<void> buildDeclarationsForClass(
      ClassDeclaration clazz, MemberDeclarationBuilder builder) async {
        final className = clazz.identifier.name;
      for(final variant in variants) {
        final match = variantRegex.firstMatch(variant);
        if (match == null) {
          throw Exception("Variant `$variant` is not valid");
        }
        final newTypeName = match.group(1)!;
        final fieldTypes = match.group(2)!.split(',').map((s) => s.trim()).toList();
        int count = 1;
        final constructor = StringBuffer();
        for(final fieldType in fieldTypes) {
          constructor.write("$fieldType v$count,");
        }
        builder.declareInType(DeclarationCode.fromString("factory $className.$newTypeName($constructor);"));
      }
  }

  @override
  Future<void> buildDefinitionForClass(
      ClassDeclaration clazz, TypeDefinitionBuilder builder) async {
        final className = clazz.identifier.name;
        final constructors = await builder.constructorsOf(clazz);
        for (final constructor in constructors) {
          final constructorName = constructor.identifier.name;
          final constructorBuilder = await builder.buildConstructor(constructor.identifier);
          constructorBuilder.augment(body: FunctionBodyCode.fromString("= $className\$$constructorName._;"));
        }
  }
}

Used like

@Enum("Variant(int)")
sealed class W {
}

void main() {
  final w = W.Variant(1);
}

Gives the following error

org-dartlang-augmentation:/workspaces/algebraic_types/bin/algebraic_types.dart-1:3:18: Error: A 'sealed' class can't be marked 'abstract' because it's already implicitly abstract.
Try removing the 'abstract' keyword.
augment abstract sealed class W {
                 ^^^^^^
org-dartlang-augmentation:/workspaces/algebraic_types/bin/algebraic_types.dart-1:4:27: Error: Expected a function body or '=>'.
Try adding {}.
factory W.Variant(int v1,);
                          ^
org-dartlang-augmentation:/workspaces/algebraic_types/bin/algebraic_types.dart-2:5:18: Error: A 'sealed' class can't be marked 'abstract' because it's already implicitly abstract.
Try removing the 'abstract' keyword.
augment abstract sealed class W {
                 ^^^^^^
org-dartlang-augmentation:/workspaces/algebraic_types/bin/algebraic_types.dart-2:6:19: Error: Constructor 'W.Variant' conflicts with an existing constructor of the same name in the augmented class.
Try changing the name of the constructor or adding an 'augment' modifier.
  augment factory W.Variant(prefix0.int v1, ) = W$Variant._;
                  ^
org-dartlang-augmentation:/workspaces/algebraic_types/bin/algebraic_types.dart-1:4:9: Context: This is the existing constructor.
factory W.Variant(int v1,);

Dart info

#### General info

- Dart 3.7.0-232.0.dev (dev) (None) on "linux_x64"
- on linux / Linux 6.6.63 #1-NixOS SMP PREEMPT_DYNAMIC Fri Nov 22 14:38:37 UTC 2024
- locale is en_US.UTF-8

#### Project info

- sdk constraint: '3.7.0-232.0.dev'
- dependencies: json
- dev_dependencies: lints, test

[dart-github-bot]

Summary: Macro-generated code adds abstract to sealed class augmentations, causing compilation errors. The abstract keyword is redundant and conflicts with the implicit abstract nature of sealed classes.