anchor.diff:      assert(modifiers == null); // TODO(paulberry)
       analyzer.Token abstractKeyword;
       List<Annotation> metadata = pop();
  -    Comment comment = null; // TODO(paulberry)
  +    // TODO(paulberry): capture doc comments.  See dartbug.com/28851.
  +    Comment comment = null;
       push(ast.classTypeAlias(
           comment,
           metadata,
  
positive.code:     debugEvent("Part");
      StringLiteral uri = pop();
      List<Annotation> metadata = pop();
      Comment comment = null; // TODO(paulberry)
      push(ast.partDirective(comment, metadata, toAnalyzerToken(partKeyword), uri,
          toAnalyzerToken(semicolon)));
    }
  
negative.code:     var modifiers = pop();
      assert(modifiers == null); // TODO(paulberry)
      List<Annotation> metadata = pop();
      // TODO(paulberry): capture doc comments.  See dartbug.com/28851.
      Comment comment = null;
      push(ast.topLevelVariableDeclaration(
          comment, metadata, variableList, toAnalyzerToken(endToken)));
    }
  