 r' = RApp c (ts ++ ts') (rs ++ rs') (r `meet` r')
tyApp t                []  []
tyApp (RApp c ts rs r) ts' rs' r' = RApp c (ts ++ ts') (rs ++ rs') (r `meet` r')
tyApp (RApp c ts rs r) ts' rs' r' = RApp c (ts ++ ts') (rs ++ rs') (r `meet` r')