In Issue #1170 we decided to add a functional pseudo-class that is exactly like :matches() but has zero specificity. However, we didn't decide on a name.

Suggestions in that thread included :is(), :when(), :filter(), and :nospecificity(). It was noted that having :filter() as a selector and filter s a property might be confusing, and that :nospecificity() is a pain to type. Additional suggestions, comments, and clarifications welcome.