extendCtsList :: Cts -> [Ct] -> Cts
extendCtsList cts xs | null xs   = cts
                     | otherwise = cts `unionBags` listToBag xs
extendCtsList :: Cts -> [Ct] -> Cts
extendCtsList cts xs | null xs   = cts
                     | otherwise = cts `unionBags` listToBag xs
extendCtsList cts xs | null xs   = cts
                     | otherwise = cts `unionBags` listToBag xs