[Haskell-cafe] Type alias in constraints

Hi, I have been using constraints of the form: xxx :: forall x xs ys zs m. ( Monad m , zs ~ Union (Filter x xs) ys , Catchable x xs , Liftable (Filter x xs) zs , Liftable ys zs ) => Variant xs -> (x -> Flow m ys) -> Flow m zs Where "zs" is used as a type alias. Now with GHC8 and -Wredundant-constraints, GHC complaints that "zs" is redundant (indeed it is). Is there a way to do this properly? If not, could we introduce a new syntax to make this kind of local declaration? We could borrow the syntax of local declarations into list-comprehensions: "let zs ~ ..." Thanks, Sylvain