Dec 2001 Hugs balks at the following simple program, while ghc 5.02.1 likes it just fine. module Tst where t1 :: (Num a) => Int -> ((?z :: Int) => a) -> a t1 w imp = imp with ?z = w The Hugs error message: ERROR "f:/Shader/tst.hs":3 - Inferred type is not general enough *** Expression : t1 *** Expected type : Num a => Int -> ((?z :: Int) => a) -> a *** Inferred type : Num Int => Int -> ((?z :: Int) => a) -> Int I can eliminate the error message by making the function be monomorphic or by eliminating the first argument and using a numeric literal, i.e., hugs likes the following just fine: t2 :: Int -> ((?z :: Int) => String) -> String t2 w imp = imp with ?z = w t3 :: (Num a) => ((?z :: Int) => a) -> a t3 imp = imp with ?z = 3 - Conal