Singletons/Empty.hs:0:0: Splicing declarations
    singletons [d| data Empty |]
  ======>
    Singletons/Empty.hs:(0,0)-(0,0)
    data Empty
    data instance Sing (z :: Empty)
    type SEmpty (z :: Empty) = Sing z
    instance SingKind (KProxy :: KProxy Empty) where
      type DemoteRep (KProxy :: KProxy Empty) = Empty
      fromSing z
        = case z of {
            _ -> error "Empty case reached -- this should be impossible" }
      toSing z
        = case z of {
            _ -> error "Empty case reached -- this should be impossible" }