Cannot extend freezed classes

[SeriousMonk]

Following documentation and the example provided in this discussion I have the following implementation.

// pagination_options.dart

import 'package:freezed_annotation/freezed_annotation.dart';

part 'pagination_options.freezed.dart';
part 'pagination_options.g.dart';

enum SortDirection {
  asc, //ascending
  desc //descending
}

@Freezed(makeCollectionsUnmodifiable: false)
abstract class PaginationOptions with _$PaginationOptions {
  const PaginationOptions._();

  const factory PaginationOptions({
    /// Page number to fetch
    @Default(1) int page,

    /// How many items per page
    @Default(20) int limit,

    /// Optional search/query string
    String? query,

    /// Sorting map: key = field name, value = ascending?
    @Default({}) Map<String, SortDirection> sort,

    /// Optional filters by key/value
    @Default({}) Map<String, dynamic> filters,
  }) = _PaginationOptions;

  factory PaginationOptions.fromJson(Map<String, dynamic> json) =>
      _$PaginationOptionsFromJson(json);
}

and then

// service_pagination_options.dart

import 'package:freezed_annotation/freezed_annotation.dart';

import '../../../general/api/shared/pagination_options.dart';

part 'service_pagination_options.freezed.dart';
part 'service_pagination_options.g.dart';

@Freezed(makeCollectionsUnmodifiable: false)
abstract class ServicePaginationOptions extends PaginationOptions with _$ServicePaginationOptions {
  const ServicePaginationOptions._() : super._();

  const factory ServicePaginationOptions({
    /// Page number to fetch
    @Default(1) int page,

    /// How many items per page
    @Default(20) int limit,

    /// Optional search/query string
    String? query,

    /// Sorting map: key = field name, value = ascending?
    @Default({}) Map<String, SortDirection> sort,

    /// Optional filters by key/value
    @Default({}) Map<String, dynamic> filters,

    /// Keys of the services to **include** in the paginated result.
    /// If null, no include filter is applied.
    List<String>? keys,

    /// Keys of the services to **exclude** from the paginated result.
    /// If null, no exclusion filter is applied.
    List<String>? excludeKeys,
  }) = _ServicePaginationOptions;

  factory ServicePaginationOptions.fromJson(Map<String, dynamic> json) =>
      _$ServicePaginationOptionsFromJson(json);
}

However i am getting the following errors in service_pagination_options.dart:

'_$ServicePaginationOptions.copyWith' ('$ServicePaginationOptionsCopyWith<ServicePaginationOptions> Function()') isn't a valid override of '_$PaginationOptions.copyWith' ('$PaginationOptionsCopyWith<PaginationOptions> Function()'). (Documentation)

The member being overridden (pagination_options.freezed.dart:28).

The class 'PaginationOptions' doesn't have a constructor named '_'. (Documentation)

Try defining a constructor named '_' in 'PaginationOptions', or invoking a different constructor.

I am using freezed: ^3.2.3 and am on flutter 3.38.2.

[SeriousMonk]

Fixed! After losing 2 days on this I found that placing the two classes in the same file solved the problem.

It should probably be explained clearly in the documentation.