anchor.diff:    final QueryProvider<K, R> provider;
   
     R call(QueryContext context, K key) {
  +    final result = context.callQuery(this, key);
  +    assert(result != null);
  +    return result;
  +  }
  +
  +  R execute(QueryContext context, K key) {
       final result = provider(context, key);
       assert(result != null);
       return result;
  
positive.code:   final QueryConfig config;
  
    Option<R> callQuery<K, R>(Query<K, R> query, K key) {
      final innerContext = QueryContext(this);
      try {
        return Option.some(innerContext.callQuery(query, key));
      } on _QueryFailedException {
        return Option.none();
      }
    }
  
    final Map<Tuple2<String, dynamic>, List<ReportedCompilerError>>
  
negative.code: import 'errors.dart';
  import 'resource_provider.dart';
  import 'utils.dart';
  
  part 'query.freezed.dart';
  part 'query.g.dart';
  
  @immutable
  class QueryConfig {
  