anchor.diff:  }
   
   class AsyncBuildError extends BuildError {
  +  AsyncBuildError([String message]) : super(message);
  +
     Future<BuildError> resolve() => Future.value(this);
   }
   
  
positive.code: import 'package:analyzer/analyzer.dart';
  import 'package:analyzer/dart/analysis/results.dart';
  import 'package:analyzer/dart/element/element.dart';
  import 'package:analyzer/error/error.dart';
  import 'package:analyzer/src/dart/analysis/results.dart';
  
negative.code: 
  class ErrorMessageForAnnotation extends AsyncBuildError {
    final IndexedAnnotation indexedAnnotation;
  
    ErrorMessageForAnnotation(
      this.indexedAnnotation,
      String message,
    ) : super(message);
  
    /// Find the ancestor node that should have the metadata and return
    /// that metadata.
  