can you please explain what the actual problem here is? i am trying to read through that issue discussion, but i am not quite getting what makes first-class fun

can you please explain what the actual problem here is? i am trying to read through that issue discussion, but i am not quite getting what makes first-class functions problematic. as far as i am concerned, not having first-class functions would be a serious limitation to a language that would make me avoid using that language for anything serious.