1 {-# LANGUAGE TypeFamilies #-}

3 -- #8883

12 -- For fold we infer following type signature:

13 --

14 -- fold :: (Functor (PF a), Regular a) => (PF a b -> b) -> a -> b

15 --

16 -- However, this signature requires FlexibleContexts since the first

17 -- type-class constraint is not of the form (class type-variable) nor

18 -- (class (type-variable type1 type2 ... typen)). Since this extension

19 -- is not enabled compilation should fail.