Add Python 3.15 TypedDict attributes (#15887)

* Add Python 3.15 TypedDict attributes

* Use AnnotationForm for TypedDict extra items

Author: charliermarsh

stdlib/_typeshed/_type_checker_internals.pyi

@@ -5,6 +5,7 @@
 import sys
 import typing_extensions
 from _collections_abc import dict_items, dict_keys, dict_values
+from _typeshed import AnnotationForm
 from abc import ABCMeta
 from collections.abc import Awaitable, Generator, Iterable, Mapping
 from typing import Any, ClassVar, Generic, TypeVar, overload
@@ -28,6 +29,10 @@ class TypedDictFallback(Mapping[str, object], metaclass=ABCMeta):
     if sys.version_info >= (3, 13):
         __readonly_keys__: ClassVar[frozenset[str]]
         __mutable_keys__: ClassVar[frozenset[str]]
+    if sys.version_info >= (3, 15):
+        # PEP 728
+        __closed__: ClassVar[bool | None]
+        __extra_items__: ClassVar[AnnotationForm]
 
     def copy(self) -> typing_extensions.Self: ...
     # Using Never so that only calls using mypy plugin hook that specialize the signature

stdlib/typing.pyi

@@ -1082,6 +1082,10 @@ class _TypedDict(Mapping[str, object], metaclass=ABCMeta):
     if sys.version_info >= (3, 13):
         __readonly_keys__: ClassVar[frozenset[str]]
         __mutable_keys__: ClassVar[frozenset[str]]
+    if sys.version_info >= (3, 15):
+        # PEP 728
+        __closed__: ClassVar[bool | None]
+        __extra_items__: ClassVar[Any]  # AnnotationForm
 
     def copy(self) -> typing_extensions.Self: ...
     # Using Never so that only calls using mypy plugin hook that specialize the signature