Fails when generating copywith for class with private fields

[haidarmehsen]

I have this class

@CopyWith(
  constructor: '_',
  skipFields: true,
)
class AppProduct {
  /// The id of the product.
  final int id;

  /// The name of the product.
  final String name;

  /// The description of the product.
  final String? description;

  /// The original price of the product.
  final double originalPrice;

  /// The discounted price of the product.
  final double? discountedPrice;

  /// The category id of the product.
  final int categoryId;

  /// The subcategory id of the product.
  final int? subcategoryId;

  /// The image URL of the product.
  final String imageURL;

  /// The type of the product.
  // ignore: invalid_annotation_target
  @JsonKey(
    fromJson: ProductType.productTypeFromProductTypeId,
    toJson: ProductType.productTypeToProductTypeId,
    name: 'productTypeId',
  )
  final ProductType productType;

  /// Whether the product is a favorite or not. This will be null if there is
  /// no user logged in.
  final bool isFavorite;

  /// The variant options of the product.
  // ignore: invalid_annotation_target
  @JsonKey(
    name: 'variants',
    fromJson: Variant.fromJsonList,
    toJson: Variant.toJsonList,
  )
  final List<Variant>? variants;

  /// Maps the id of a single-choice-option variant to the id of the selected option of that variant.
  @JsonKey(
    name: 'singleSelectionOptions',
    defaultValue: {},
    includeToJson: true,
    includeFromJson: true,
  )
  final Map<int, int> _singleSelectionOptions;

  /// Maps the id of a multiple-choice-option variant to the ids of the selected options of that variant.
  @JsonKey(
    name: 'multipleSelectionOptions',
    defaultValue: {},
    includeToJson: true,
    includeFromJson: true,
  )
  final Map<int, List<int>> _multipleSelectionOptions;

  AppProduct._(
    this._singleSelectionOptions,
    this._multipleSelectionOptions, {
    required this.id,
    required this.name,
    this.description,
    required this.originalPrice,
    this.discountedPrice,
    required this.categoryId,
    this.subcategoryId,
    required this.imageURL,
    required this.productType,
    required this.isFavorite,
    this.variants,
  }) {
    _ensureRequiredOptionsSelected();
  }
}

The IDE reports no erros in the generated code, but when trying to run the app, I get this error and the app can't start:

lib/services/api/product_management_service/app_product/app_product.g.dart:17:20: Error: An optional named parameter can't start with '_'.
    Map<int, int>? _singleSelectionOptions,
                   ^^^^^^^^^^^^^^^^^^^^^^^
lib/services/api/product_management_service/app_product/app_product.g.dart:18:26: Error: An optional named parameter can't start with '_'.
    Map<int, List<int>>? _multipleSelectionOptions,
                         ^^^^^^^^^^^^^^^^^^^^^^^^^
lib/services/api/product_management_service/app_product/app_product.g.dart:48:13: Error: An optional named parameter can't start with '_'.
    Object? _singleSelectionOptions = const $CopyWithPlaceholder(),
            ^^^^^^^^^^^^^^^^^^^^^^^
lib/services/api/product_management_service/app_product/app_product.g.dart:49:13: Error: An optional named parameter can't start with '_'.
    Object? _multipleSelectionOptions = const $CopyWithPlaceholder(),
            ^^^^^^^^^^^^^^^^^^^^^^^^^