I'm puzzled by GHC's behaviour in the following program. 'baz = bar . foo' does not work because there is "no instance for ...". But if I manually assume those instances in the context all is fine. Why can GHC not infer that context? Is there any extension or clever trick I can use to get this to infer like I want? Thanks, Tom {-# LANGUAGE MultiParamTypeClasses #-} {-# LANGUAGE TypeFamilies #-} {-# LANGUAGE FlexibleContexts #-} class Foo a b class Bar a b type family Quux a foo :: ( Foo a b , b ~ Quux a ) => a -> Quux a foo = undefined bar :: Bar a b => a -> b bar = undefined -- Doesn't work -- No instance for (Bar (Quux a0) c0) arising from a use of ‘bar’ -- No instance for (Foo a0 (Quux a0)) arising from a use of ‘foo’ --baz = bar . foo baz' :: ( Foo a (Quux a) , Bar (Quux a) b ) => a -> b baz' = bar . foo