tcfail117.hs:6:32: error:
    • Can't make a derived instance of ‘Enum N1’:
        ‘N1’ must be an enumeration type
        (an enumeration consists of one or more nullary, non-GADT constructors)
        Try GeneralizedNewtypeDeriving for GHC's newtype-deriving extension
    • In the newtype declaration for ‘N1’

tcfail117.hs:7:32: error:
    • Can't make a derived instance of ‘Enum N2’:
        ‘N2’ must be an enumeration type
        (an enumeration consists of one or more nullary, non-GADT constructors)
    • In the data declaration for ‘N2’