diff --git a/pandas/core/reshape/merge.py b/pandas/core/reshape/merge.py index 46b2e5d29d247..9a534ef7625a4 100644 --- a/pandas/core/reshape/merge.py +++ b/pandas/core/reshape/merge.py @@ -1648,16 +1648,13 @@ def get_result(self) -> DataFrame: right_join_indexer: np.ndarray | None if self.fill_method == "ffill": - # error: Argument 1 to "ffill_indexer" has incompatible type - # "Optional[ndarray]"; expected "ndarray" - left_join_indexer = libjoin.ffill_indexer( - left_indexer # type: ignore[arg-type] - ) - # error: Argument 1 to "ffill_indexer" has incompatible type - # "Optional[ndarray]"; expected "ndarray" - right_join_indexer = libjoin.ffill_indexer( - right_indexer # type: ignore[arg-type] + if left_indexer is None: + raise TypeError("left_indexer cannot be None") + left_indexer, right_indexer = cast(np.ndarray, left_indexer), cast( + np.ndarray, right_indexer ) + left_join_indexer = libjoin.ffill_indexer(left_indexer) + right_join_indexer = libjoin.ffill_indexer(right_indexer) else: left_join_indexer = left_indexer right_join_indexer = right_indexer