add test to cover passing UnknownSeries to cat

Author: MarcoGorelli

pandas-stubs/_typing.pyi

@@ -576,9 +576,6 @@ S2 = TypeVar(
     | list[str],
 )
 
-UnknownSeries: TypeAlias = Series[Any]
-UnknownIndex: TypeAlias = Index[Any]
-
 IndexingInt: TypeAlias = (
     int | np.int_ | np.integer | np.unsignedinteger | np.signedinteger | np.int8
 )

pandas-stubs/core/indexes/base.pyi

@@ -13,6 +13,7 @@ from typing import (
     Any,
     ClassVar,
     Literal,
+    TypeAlias,
     final,
     overload,
 )
@@ -455,7 +456,7 @@ class Index(IndexOpsMixin[S1]):
         ),
     ) -> Self: ...
 
-class UnknownIndex(Index[Any]): ...
+UnknownIndex: TypeAlias = Index[Any]
 
 def ensure_index_from_sequences(
     sequences: Sequence[Sequence[Dtype]], names: list[str] = ...

pandas-stubs/core/series.pyi

@@ -2295,3 +2295,5 @@ class IntervalSeries(Series[Interval[_OrderableT]], Generic[_OrderableT]):
     @property
     def array(self) -> IntervalArray: ...
     def diff(self, periods: int = ...) -> Never: ...
+
+UnknownSeries: TypeAlias = Series[Any]

tests/test_series.py

@@ -65,9 +65,8 @@
         OffsetSeries,
         TimedeltaSeries,
         TimestampSeries,
+        UnknownSeries,
     )
-
-    from pandas._typing import UnknownSeries
 else:
     TimedeltaSeries: TypeAlias = pd.Series
     TimestampSeries: TypeAlias = pd.Series
@@ -1681,6 +1680,11 @@ def test_series_overloads_cat():
         ),
         UnknownSeries,
     )
+    unknown_s: UnknownSeries = pd.DataFrame({"a": ["a", "b"]})["a"]
+    check(
+        assert_type(s.str.cat(unknown_s, sep=";"), UnknownSeries),
+        UnknownSeries,
+    )
 
 
 def test_series_overloads_partition():