I actually don't know. The only change introduced by here is that type annotations are not eliminated.

Actually I probably got it wrong in my comment: "eliminates singleton types using _.underlying". Underlying means all kinds of different things (for ThisType, AnnotatedType, ConstantType, TypeProxy, ...) and I'm quite sure now that the person who wrote the code should have picked something else than `underlying` here. But I'm not sure what was the intention..