(forall a. Bounded a => f0 a) -> h0 f0 xs0 GHC doesn't yet support impredicative polymorphism • In the second argument of ‘(&)’, namely ‘hcpure (Proxy @Bounded)’ In the expression: (&) minBound hcpure (Proxy @Bounded) In an equation for ‘a’: a = (&) minBound hcpure (Proxy @Bounded)