anchor.diff:      var library = resolver.getLibrary(inputId);
       log.warning(
           'Investigating library ${library.exportNamespace.definedNames.keys}');
  -    library.visitChildren(new DeepEqualityVisitor());
  +    var visitor = new DeepEqualityVisitor();
  +    library.visitChildren(visitor);
  +    if (visitor.descriptionGenerators.isNotEmpty) {
  +      // write output.
  +      var outStr = "import 'package:${inputId.package}/${inputId.path}';\n";
  +      for (var generator in visitor.descriptionGenerators) {
  +        outStr += '\n';
  +        outStr += generator.generatedCode;
  +      }
  +      log.warning(outStr);
  +      buildStep.writeAsString(outputId, outStr);
  +    }
     }
   
     @override
  
positive.code:     for (var field in element.fields) {
        log.warning('Found field $field');
      }
      log.warning(new DescriptionGenerator(element).generatedCode);
    }
  }
  
  
negative.code: class DeepEqualityVisitor extends SimpleElementVisitor {
    static const deepEqualityKey = const _UniqueKey(
        'asset:compiled_mirrors/lib/compiled_mirrors.dart', 'CompileMirror');
    final List<DescriptionGenerator> descriptionGenerators =
        <DescriptionGenerator>[];
  
    DeepEqualityVisitor();
  
  