
tcfail201.hs:18:28:
    Couldn't match type `a' with `HsDoc id0'
      `a' is a rigid type variable bound by
          the type signature for
            gfoldl' :: (forall a1 b. c (a1 -> b) -> a1 -> c b)
                       -> (forall g. g -> c g) -> a -> c a
          at tcfail201.hs:16:1
    In the pattern: DocParagraph hsDoc
    In a case alternative:
        (DocParagraph hsDoc) -> z DocParagraph `k` hsDoc
    In the expression:
      case hsDoc of {
        DocEmpty -> z DocEmpty
        (DocParagraph hsDoc) -> z DocParagraph `k` hsDoc }
