Weak

When the right hand side of a nonterminal is formed from several symbols that happen to occur one after another, without forming a proper abstraction, this can hinder grammar’s understanding.

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.