:2:10: error: • Found hole: _ :: f a Where: ‘f’ is a rigid type variable bound by the inferred type of it :: Functor f => f (Maybe a) at :2:1 ‘a’ is a rigid type variable bound by the inferred type of it :: Functor f => f (Maybe a) at :2:1 • In the second argument of ‘(<$>)’, namely ‘_’ In the expression: Just <$> _ In an equation for ‘it’: it = Just <$> _ • Relevant bindings include it :: f (Maybe a) (bound at :2:1)