Hi,
I just found out that with the new ConstraintKinds extension we can
parameterize the constraint of an existentially quantified type:
{-# LANGUAGE KindSignatures, ConstraintKinds, ExistentialQuantification #-}
import GHC.Exts
data Some (c :: * -> Constraint) = forall a. c a => Some a
This could be used to define SomeException for example:
import Control.Exception (Exception)
type SomeException = Some Exception
Are there any other use cases?
Bas
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