Macros: Are macros compatible with class modifiers?

[felangel]

I'm wondering whether it's possible to use class modifiers (e.g. sealed, final, etc.) with macros.

Steps to reproduce:

1. Clone https://github.com/felangel/struct
2. Run the example dart --enable-experiment=macros run example/main.dart
3. Note that it runs fine
4. Add the sealed class modifier to example/main.dart

   import 'package:struct_annotation/struct_annotation.dart';
   
   @Struct()
   + sealed class Person {
   - class Person {
     final String name;
     final int age;
   }
   
   void main() {
     final jane = Person(name: 'Jane', age: 42);
     final john = jane.copyWith(name: 'John');
   
     print(jane); // Person(name: Jane, age: 42)
     print(john); // Person(name: John, age: 42)
   
     print(jane == jane.copyWith()); // true
     print(john == john.copyWith(age: 21)); // false
   }

5. Run the example again
6. Observe error:

   dart --enable-experiment=macros run example/main.dart     
   org-dartlang-augmentation:/struct/example/main.dart-0:3:18: Error: A 'sealed' class can't be marked 'abstract' because it's already implicitly abstract.
   Try removing the 'abstract' keyword.
   augment abstract sealed class Person {
                    ^^^^^^
   org-dartlang-augmentation:/struct/example/main.dart-1:7:18: Error: A 'sealed' class can't be marked 'abstract' because it's already implicitly abstract.
   Try removing the 'abstract' keyword.
   augment abstract sealed class Person {
                    ^^^^^^
   org-dartlang-augmentation:/struct/example/main.dart-1:10:82: Error: The class 'Person' is abstract and can't be instantiated.
     augment prefix1.Person copyWith({prefix0.String? name, prefix0.int? age, }) => Person(name: name ?? this.name,age: age ?? this.age,);
                                                                                    ^^^^^^
   example/main.dart:10:16: Error: The class 'Person' is abstract and can't be instantiated.
     final jane = Person(name: 'Jane', age: 42);
   

[lrhn]

That looks like two problems.

One is the abstract which shouldn't be there. That's probably a bug in the macros implementation.

The other is that the Struct macro tries to generate a copyWith on an abstract class. That's a bug in that macro, or at least something that can do with a better error message, since it's not possible.

[felangel]

That looks like two problems.

One is the abstract which shouldn't be there. That's probably a bug in the macros implementation.

The other is that the Struct macro tries to generate a copyWith on an abstract class. That's a bug in that macro, or at least something that can do with a better error message, since it's not possible.

The copyWith implementation generated by the Struct macro appears to work just fine but yeah I agree that the abstract likely shouldn't be there (that was mainly what I was confused about).

[felangel]

This appears to go away when I import the the macro directly from src: Dart-Code/Dart-Code#5110 (comment).

Closing this since it seems to be fixed already in #55746. Thanks for the quick response!