T12478_4.hs:7:7: error: [GHC-97721]
    • Illegal sum arity: 1
        Sums must have an arity of at least 2
      When splicing a TH type: (#  #) GHC.Tuple.Prim.()
    • In the untyped splice: $(unboxedSumT 1 `appT` conT ''())