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

[flicky frans]

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.