anchor.diff:        astNode.isSynthetic ? '' : astNode.sourceSpan.start.toString();
   }
   
  -class ParseContext {}
  +class ParseContext {
  +  final String elementName;
  +
  +  ParseContext({this.elementName});
  +
  +  ParseContext withElementName(String name) =>
  +      new ParseContext(elementName: name);
  +}
   
   /// Visitor which filters elements that are not supported in angular templates.
   class ElementFilter implements ast.TemplateAstVisitor<ast.TemplateAst, bool> {
  
positive.code: 
    @override
    ng.TemplateAst visitEmbeddedTemplate(ast.EmbeddedTemplateAst astNode,
            [ParseContext context]) =>
        new ng.EmbeddedTemplateAst(
            _visitAll(astNode.attributes, context),
            _visitAll(astNode.events, context),
            _visitAll(astNode.references, context),
            _visitAll(astNode.letBindings, context),
            [] /* directives */,
            [] /* providers */,
            null /* elementProviderUsage */,
            _visitAll(astNode.childNodes, context),
            0 /* ngContentIndex */,
            astNode.sourceSpan);
  
    @override
    ng.TemplateAst visitEvent(ast.EventAst astNode, [ParseContext _]) {
  
negative.code:       throw new UnimplementedError('Don\'t know how to handle comments.');
  
    @override
    ng.TemplateAst visitElement(ast.ElementAst astNode, [ParseContext context]) {
      final elementContext = context.withElementName(astNode.name);
      return new ng.ElementAst(
          astNode.name,
          _visitAll(astNode.attributes, elementContext),
          _visitAll(astNode.properties, elementContext),
          _visitAll(astNode.events, elementContext),
          _visitAll(astNode.references, elementContext),
          [] /*directives */,
          [] /* providers */,
          null /* elementProviderUsage */,
          _visitAll(astNode.childNodes, elementContext),
          0 /* ngContentIndex */,
          astNode.sourceSpan);
    }
  
    @override
    ng.TemplateAst visitEmbeddedContent(ast.EmbeddedContentAst astNode,
  