ppr_co p (TcSubCo co)         = pprPrefixApp p (ptext (sLit "Sub")) [pprParendTcCo co]
ppr_co p (TcSubCo co)         = pprPrefixApp p (ptext (sLit "Sub")) [pprParendTcCo co]
ppr_co p (TcSubCo co)         = pprPrefixApp p (ptext (sLit "Sub")) [pprParendTcCo co]