# Pastebin 8j1d1vT0
Given:

data Bar f = Bar (f [Int]) deriving Generic
deriving via Generically (Bar f) instance (forall a . Semigroup a => Semigroup (f a)) => Semigroup (Bar f)
deriving via Generically (Bar f) instance (forall a . Monoid a => Monoid (f a)) => Monoid (Bar f)

GHC accepts the first instance declaration but rejects the second with:

    • Could not deduce (Monoid a)
        arising from the superclasses of an instance declaration
      from the context: forall a. Monoid a => Monoid (f a)
        bound by the instance declaration at <loc>
      or from: Semigroup a
        bound by a quantified context at <loc>
      Possible fix: add (Monoid a) to the context of a quantified context
    • In the instance declaration for ‘Monoid (Bar f)’