Revert "use S2 python/mypy#19182"

This reverts commit 1c0f351.

Author: MarcoGorelli

pandas-stubs/_typing.pyi

@@ -824,8 +824,30 @@ MaskType: TypeAlias = Series[bool] | np_ndarray_bool | list[bool]
 
 # Scratch types for generics
 
-SeriesDType: TypeAlias = (
-    str
+S1 = TypeVar(
+    "S1",
+    bound=str
+    | bytes
+    | datetime.date
+    | datetime.time
+    | bool
+    | int
+    | float
+    | complex
+    | Dtype
+    | datetime.datetime  # includes pd.Timestamp
+    | datetime.timedelta  # includes pd.Timedelta
+    | Period
+    | Interval
+    | CategoricalDtype
+    | BaseOffset
+    | list[str],
+    default=Any,
+)
+
+S2 = TypeVar(
+    "S2",
+    bound=str
     | bytes
     | datetime.date
     | datetime.time
@@ -840,11 +862,8 @@ SeriesDType: TypeAlias = (
     | Interval
     | CategoricalDtype
     | BaseOffset
-    | list[str]
+    | list[str],
 )
-S1 = TypeVar("S1", bound=SeriesDType, default=Any)
-# Like S1, but without `default=Any`.
-S2 = TypeVar("S2", bound=SeriesDType)
 
 IndexingInt: TypeAlias = (
     int | np.int_ | np.integer | np.unsignedinteger | np.signedinteger | np.int8

pandas-stubs/core/frame.pyi

@@ -136,7 +136,6 @@ from pandas._typing import (
     ScalarT,
     SequenceNotStr,
     SeriesByT,
-    SeriesDType,
     SortKind,
     StataDateFormat,
     StorageOptions,
@@ -1392,23 +1391,13 @@ class DataFrame(NDFrame, OpsMixin, _GetItemHack):
     @overload
     def apply(
         self,
-        f: Callable[..., S2],
+        f: Callable[..., S2 | NAType],
         axis: AxisIndex = ...,
         raw: _bool = ...,
         result_type: None = ...,
         args: Any = ...,
         **kwargs: Any,
     ) -> Series[S2]: ...
-    @overload
-    def apply(
-        self,
-        f: Callable[..., SeriesDType | NAType],
-        axis: AxisIndex = ...,
-        raw: _bool = ...,
-        result_type: None = ...,
-        args: Any = ...,
-        **kwargs: Any,
-    ) -> Series: ...
     # Since non-scalar type T is not supported in Series[T],
     # we separate this overload from the above one
     @overload
@@ -1426,7 +1415,7 @@ class DataFrame(NDFrame, OpsMixin, _GetItemHack):
     @overload
     def apply(
         self,
-        f: Callable[..., S2],
+        f: Callable[..., S2 | NAType],
         axis: Axis = ...,
         raw: _bool = ...,
         args: Any = ...,
@@ -1435,17 +1424,6 @@ class DataFrame(NDFrame, OpsMixin, _GetItemHack):
         **kwargs: Any,
     ) -> Series[S2]: ...
     @overload
-    def apply(
-        self,
-        f: Callable[..., SeriesDType | NAType],
-        axis: Axis = ...,
-        raw: _bool = ...,
-        args: Any = ...,
-        *,
-        result_type: Literal["expand", "reduce"],
-        **kwargs: Any,
-    ) -> Series: ...
-    @overload
     def apply(
         self,
         f: Callable[..., ListLikeExceptSeriesAndStr | Series | Mapping[Any, Any]],
@@ -1495,11 +1473,10 @@ class DataFrame(NDFrame, OpsMixin, _GetItemHack):
     ) -> Series: ...
 
     # apply() overloads with default result_type of None, and keyword axis=1 matters
-    # Use S2 (TypeVar without the `Any` default) to avoid MyPy issue https://github.com/python/mypy/issues/19182.
     @overload
     def apply(
         self,
-        f: Callable[..., S2],
+        f: Callable[..., S2 | NAType],
         raw: _bool = ...,
         result_type: None = ...,
         args: Any = ...,
@@ -1508,17 +1485,6 @@ class DataFrame(NDFrame, OpsMixin, _GetItemHack):
         **kwargs: Any,
     ) -> Series[S2]: ...
     @overload
-    def apply(
-        self,
-        f: Callable[..., SeriesDType | NAType],
-        raw: _bool = ...,
-        result_type: None = ...,
-        args: Any = ...,
-        *,
-        axis: AxisColumn,
-        **kwargs: Any,
-    ) -> Series: ...
-    @overload
     def apply(
         self,
         f: Callable[..., ListLikeExceptSeriesAndStr | Mapping[Any, Any]],