Ouroboros

If nonterminals are mutually, say, left recursive, and have no non-recursive alternatives, they are useless and cannot express a proper syntactic commitment. However, a similar issue may be encountered on the level of modules, and it is harder to detect for a human because modular grammars are already stretching comprehension capabilities of a grammar engineer.

Reference

Mats Stijlaart and Vadim Zaytsev. 2017. Towards a taxonomy of grammar smells. In Proceedings of the 10th ACM SIGPLAN International Conference on Software Language Engineering (SLE 2017). ACM, New York, NY, USA, 43-54.