(Erica_Sadun) > Even if the team prefers to use a () -> Never rhs, I'd still recommend using !! over ?? to indicate the imbalance in roles between the safely unwrapped lhs and the unsafely unwrapped rhs. Expanding Never to be a bottom type does not fix this symbology mismatch. Whether Never is or is not a bottom type is orthogonal to this proposal. (edited)