pprHsContextExtra True
  = \ctxt -> case ctxt of
               [] -> char '_' <+> darrow
               _  -> parens (sep (punctuate comma ctxt')) <+> darrow
                 where ctxt' = map ppr ctxt ++ [char '_']
pprHsContextExtra True
  = \ctxt -> case ctxt of
               [] -> char '_' <+> darrow
               _  -> parens (sep (punctuate comma ctxt')) <+> darrow
                 where ctxt' = map ppr ctxt ++ [char '_']
pprHsContextExtra True
  = \ctxt -> case ctxt of
               [] -> char '_' <+> darrow
               _  -> parens (sep (punctuate comma ctxt')) <+> darrow
                 where ctxt' = map ppr ctxt ++ [char '_']