patTyCons :: AltCon -> Set TyCon
patTyCons p = case p of
    DataAlt c -> S.singleton (dataConTyCon c)
    LitAlt{}  -> S.empty
    DEFAULT   -> S.empty
patTyCons :: AltCon -> Set TyCon
patTyCons p = case p of
    DataAlt c -> S.singleton (dataConTyCon c)
    LitAlt{}  -> S.empty
    DEFAULT   -> S.empty
patTyCons p = case p of
    DataAlt c -> S.singleton (dataConTyCon c)
    LitAlt{}  -> S.empty
    DEFAULT   -> S.empty