Re: [Haskell-beginners] How to avoid repeating a type restriction from a data constructor

Daniel Fischer writes:

Use a GADT,

{-# LANGUAGE GADTs #-}

data Source x y where Source :: Variable v => { bindings :: v [Binding a], var :: v a } -> Source v a

I tried this, but every place that I remove the restriction Variable v => from something using Source, I get an error No instance for (Variable v) ...