code: private Node parseFieldName(JsDocToken token) {
      switch (token) {
        case STRING:
          String s = stream.getString();
          Node n = Node.newString(
              Token.STRING_KEY, s, stream.getLineno(), stream.getCharno())
              .clonePropsFrom(templateNode);
          n.setLength(s.length());
          return n;
  
        default:
          return null;
      }
    }
docs: FieldName := NameExpression | StringLiteral | NumberLiteral |
  ReservedIdentifier