There is no Applicative for Forget a

[Icelandjack]

Applicative (Forget a) (and the rest of the instances) should be derived via Star (Const a)

[Icelandjack]

I tried to add the following deriving statements¹ but it produces a cyclical import for Traversing and the other classes. Does it need a restructure, or should those instances not be added?

newtype Forget r a b = Forget { runForget :: a -> r }
  deriving (Profunctor, Choice, Cochoice, Strong, Traversing) -- Rep.Representable
  via Star (Const r)

  deriving (Functor, Applicative, Contravariant)
  via Star (Const r) a

¹ How best to derive Semigroup, Monoid

[RyanGlScott]

That's somewhat unfortunate, but it should still be possible to implement the instances by hand, right? (We could leave a comment next to these instances saying that "morally", they're what deriving via Star (Const r) would give you.)