[Haskell-cafe] Partially applied type synonyms

I was surprised to find the below code doesn't typecheck even with -XLiberalTypeSynonyms. Am I missing something or is this really not possible? Thanks, Tom --- {-# LANGUAGE FlexibleInstances, KindSignatures, LiberalTypeSynonyms, StandaloneDeriving #-} -- This works: data Foo s x = Foo (s x) x deriving (Eq) -- This replacement doesn't: {- data Foo' sx x = Foo' sx x deriving (Eq) type Foo (s :: * -> *) (x :: *) = Foo' (s x) x -} data Bar (m :: * -> *) = Bar (m Int) -- Neither of these typecheck: x :: Bar (Foo Maybe) x = undefined deriving instance Eq (Bar (Foo Maybe))