
tcfail019.hs:18:10:
    No instance for (B [a])
      arising from the superclasses of an instance declaration
    Possible fix: add an instance declaration for (B [a])
    In the instance declaration for `D [a]'

tcfail019.hs:18:10:
    No instance for (C [a])
      arising from the superclasses of an instance declaration
    Possible fix: add an instance declaration for (C [a])
    In the instance declaration for `D [a]'
