Hello, I have the following program: -------------------------------------------------------------------------- {-# LANGUAGE ConstraintKinds #-} {-# LANGUAGE ExistentialQuantification #-} {-# LANGUAGE ScopedTypeVariables #-} import Data.Proxy (Proxy) import Data.Typeable (Typeable, TypeRep, typeOf) data ProxyWrapper constraint = forall a. constraint a => ProxyWrapper (Proxy a) typeOfInnerProxy :: ProxyWrapper constraint -> TypeRep typeOfInnerProxy (ProxyWrapper p) = typeOfArg p typeOfArg :: forall t a. Typeable a => t a -> TypeRep typeOfArg _ = typeOf (undefined :: a) -------------------------------------------------------------------------- Type checking this gives the following expected type error: ProxyWrapper.hs:12:37: Could not deduce (Typeable a) arising from a use of `typeOfArg' from the context (constraint a) bound by a pattern with constructor ProxyWrapper :: forall (constraint :: * -> Constraint) a. (constraint a) => Proxy a -> ProxyWrapper constraint, in an equation for `typeOfInnerProxy' Is there a way to extend the 'constraint' with the 'Typeable' constraint in the type signature of 'typeOfInnerProxy'? Regards, Bas