anchor.diff:    /// Returns and parses a top-level AST structure.
     StandaloneTemplateAst parseStandalone(
       NgToken token, [
  -    Queue<String> tagStack,
  +    List<String> tagStack,
     ]) {
  -    tagStack = tagStack ?? new Queue();
  +    tagStack ??= [];
       switch (token.type) {
         case NgTokenType.commentStart:
           return parseComment(token);
  
positive.code: // Copyright (c) 2016, the Dart project authors.  Please see the AUTHORS file
  // for details. All rights reserved. Use of this source code is governed by a
  // BSD-style license that can be found in the LICENSE file.
  
  import 'dart:collection';
  
  import 'package:source_span/source_span.dart';
  import 'package:string_scanner/string_scanner.dart';
  
negative.code:           childNodes.add(childAst);
          }
        }
        tagStack.removeLast();
      }
  
      if (isTemplateElement) {
  