pytz: utcoffset only returns None if dt is None (#7510)

Author: JelleZijlstra

stubs/pytz/pytz/tzinfo.pyi

@@ -1,6 +1,6 @@
 import datetime
 from abc import abstractmethod
-from typing import Any
+from typing import Any, overload
 
 class BaseTzInfo(datetime.tzinfo):
     zone: str | None  # Actually None but should be set on concrete subclasses
@@ -31,5 +31,9 @@ class DstTzInfo(BaseTzInfo):
     def localize(self, dt: datetime.datetime, is_dst: bool | None = ...) -> datetime.datetime: ...
     def normalize(self, dt: datetime.datetime) -> datetime.datetime: ...
     def tzname(self, dt: datetime.datetime | None, is_dst: bool | None = ...) -> str: ...
-    def utcoffset(self, dt: datetime.datetime | None, is_dst: bool | None = ...) -> datetime.timedelta | None: ...
+    # https://github.com/python/mypy/issues/12379
+    @overload  # type: ignore[override]
+    def utcoffset(self, dt: None, is_dst: bool | None = ...) -> None: ...
+    @overload
+    def utcoffset(self, dt: datetime.datetime, is_dst: bool | None = ...) -> datetime.timedelta: ...
     def dst(self, dt: datetime.datetime | None, is_dst: bool | None = ...) -> datetime.timedelta | None: ...