Re: [Haskell-cafe] Injective type families for GHC - syntax proposals

Maybe it's worth adding an explicit type variable for the result? Something like: type family Id a -> r | r -> a where type family G a b c -> res | res -> a b where type family Plus a b -> result | result a -> b, result b -> a where It's a little verbose, but certainly is not confusing, since LHS really determines RHS.