Hello, GHC 6.12.3 allows to omit the explicit quantification of higher-rank type variables using 'forall' in data types if they appear in a type class context {-# LANGUAGE RankNTypes #-} data Foo = Foo (Eq a => a) Is this implicit introduction of 'forall' intended? If it is, why does it not work in function types? The following is not accepted by my GHC: bar :: Eq b => (Eq a => a) -> b bar x = x The error message is All of the type variables in the constraint `Eq a' are already in scope (at least one must be universally quantified here) (Use -XFlexibleContexts to lift this restriction) Using `FlexibleContexts` the signature of `bar` seems to be interpreted as bar :: (Eq b, Eq a) => a -> b because then the error becomes Couldn't match expected type `b' against inferred type `a' So unlike in data-type declarations, a 'forall' in a function type must be written explicitly even if the quantified variable appears in a local type class constraint. bar :: Eq b => (forall a . Eq a => a) -> b bar x = x I have not yet installed GHC 7. Is this inconsistency between data and function declarations intended or has it been changed in the new type checker? Sebastian