I found interesting papers related to packcc. * [不完全な文法からパーサを生成する手法の検討](http://jssst.or.jp/files/user/taikai/2019/PPL/ppl3-2.pdf) (in Japanese) * [LakeSymbolsforIslandParsing](https://arxiv.org/pdf/2010.16306v1.pdf) How do you think? It looks quite useful for ctags users.