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{-# LANGUAGE DataKinds, PolyKinds, TypeFamilies, GADTs, ConstraintKinds #-}
module T12919 where
import Data.Kind
data N = Z
data V :: N -> Type where
VZ :: V Z
type family VC (n :: N) :: Type where
VC Z = Type
type family VF (xs :: V n) (f :: VC n) :: Type where
VF VZ f = f
data Dict c where
Dict :: c => Dict c
prop :: xs ~ VZ => Dict (VF xs f ~ f)
prop = Dict
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