validateDeclaration method

@override void validateDeclaration()

Implementation

@override
void validateDeclaration() {
  final allowed = allowedValues;
  if (allowed != null &&
      (allowed.isEmpty ||
          allowed.toSet().length != allowed.length ||
          !allowed.contains(defaultValue))) {
    throw ArgumentError(
      'String field requires unique options containing its default',
    );
  }
}