T9144.hs:34:26: error:
    • Couldn't match type ‘Integer’ with ‘FooTerm’
      Expected type: DemoteRep 'KProxy
        Actual type: DemoteRep 'KProxy
      Use -fprint-explicit-kinds to see the kind arguments
    • In the first argument of ‘toSing’, namely ‘n’
      In the expression: toSing n
      In the expression:
        case toSing n of { SomeSing n' -> SomeSing (SBar n') }