GADT record syntax and contexts

[Roberto Zunino]

Simon Peyton-Jones wrote:
> (A)   data RecContTest a where
>          Show a => C { showable :: Show a => a } :: RecContTest a
> 
> (B)   data RecContTest a where
>          C :: Show a => { showable :: Show a => a } -> RecContTest a

What about

   (A')  data RecContTest a where
            Show a => C { showable :: a } :: RecContTest a

   (B')  data RecContTest a where
            C :: Show a => { showable :: a } -> RecContTest a

? Would this be allowed?

I would expect A' and B' to generate

   showable :: RecContTest a -> a

and not the less useful (Show-requiring)

   showable :: Show a => RecContTest a -> a

Zun.