Index: ensure Index(DatetimeIndex) returns DatetimeIndex (fixes #1440) (#1456)

* Index: ensure Index(DatetimeIndex) returns DatetimeIndex (fixes #1440)

* Add isolated test for Index(DatetimeIndex) typing (GH#1440)

* Fix: Index(DatetimeIndex) now returns DatetimeIndex; consolidated test (fixes #1440)

* Remove redundant test_datetime_index_1440.py and run pre-commit

Author: yusufcank34

pandas-stubs/core/indexes/base.pyi

@@ -189,7 +189,9 @@ class Index(IndexOpsMixin[S1], ElementOpsMixin[S1]):
     @overload
     def __new__(
         cls,
-        data: Sequence[np.datetime64 | datetime] | IndexOpsMixin[datetime],
+        data: (
+            Sequence[np.datetime64 | datetime] | IndexOpsMixin[datetime] | DatetimeIndex
+        ),
         *,
         dtype: TimestampDtypeArg = ...,
         copy: bool = ...,
@@ -276,6 +278,16 @@ class Index(IndexOpsMixin[S1], ElementOpsMixin[S1]):
         name: Hashable = ...,
         tupleize_cols: bool = ...,
     ) -> IntervalIndex[Interval[Any]]: ...
+    @overload
+    def __new__(
+        cls,
+        data: DatetimeIndex,
+        *,
+        dtype: TimestampDtypeArg | None = ...,
+        copy: bool = ...,
+        name: Hashable = ...,
+        tupleize_cols: bool = ...,
+    ) -> DatetimeIndex: ...
     # generic overloads
     @overload
     def __new__(

tests/indexes/test_datetime_index.py

@@ -24,7 +24,7 @@ def test_index_relops() -> None:
     )
     x = pd.Timestamp("2022-01-17")
     idx = check(
-        assert_type(pd.Index(data, name="date"), "pd.Index[pd.Timestamp]"), pd.Index
+        assert_type(pd.Index(data, name="date"), pd.DatetimeIndex), pd.DatetimeIndex
     )
     check(assert_type(data[x <= idx], pd.DatetimeIndex), pd.DatetimeIndex)
     check(assert_type(data[x < idx], pd.DatetimeIndex), pd.DatetimeIndex)