Move NotImplementedType to types.pyi (#14966)

stdlib/@tests/test_cases/check_types.py

@@ -62,7 +62,21 @@ class DCAtest:
         self._value = None
 
 
-if sys.version_info > (3, 10):
+# check that NotImplemented is treated as an "Any"
+x: int = NotImplemented
+
+if sys.version_info >= (3, 10):
+    # test NotImplementedType usage
+    assert_type(NotImplemented, types.NotImplementedType)
+    assert_type(types.NotImplementedType(), types.NotImplementedType)
+    # test EllipsisType usage
+    assert_type(Ellipsis, types.EllipsisType)
+    assert_type(types.EllipsisType(), types.EllipsisType)
+    # test NoneType usage (disabled, passes with pyright, but mypy errors
+    # assert_type(None, types.NoneType)
+    # assert_type(types.NoneType(), types.NoneType)
+
+if sys.version_info >= (3, 11):
     union_type = int | list[_T]
 
     # ideally this would be `_SpecialForm` (Union)

stdlib/builtins.pyi

@@ -1367,13 +1367,6 @@ class property:
     def __set__(self, instance: Any, value: Any, /) -> None: ...
     def __delete__(self, instance: Any, /) -> None: ...
 
-@final
-@type_check_only
-class _NotImplementedType(Any):
-    __call__: None
-
-NotImplemented: _NotImplementedType
-
 def abs(x: SupportsAbs[_T], /) -> _T: ...
 def all(iterable: Iterable[object], /) -> bool: ...
 def any(iterable: Iterable[object], /) -> bool: ...
@@ -2032,14 +2025,14 @@ def __import__(
 def __build_class__(func: Callable[[], CellType | Any], name: str, /, *bases: Any, metaclass: Any = ..., **kwds: Any) -> Any: ...
 
 if sys.version_info >= (3, 10):
-    from types import EllipsisType
+    from types import EllipsisType, NotImplementedType
 
     # Backwards compatibility hack for folks who relied on the ellipsis type
     # existing in typeshed in Python 3.9 and earlier.
     ellipsis = EllipsisType
 
     Ellipsis: EllipsisType
-
+    NotImplemented: NotImplementedType
 else:
     # Actually the type of Ellipsis is <type 'ellipsis'>, but since it's
     # not exposed anywhere under that name, we make it private here.
@@ -2049,6 +2042,13 @@ else:
 
     Ellipsis: ellipsis
 
+    @final
+    @type_check_only
+    class _NotImplementedType(Any):
+        __call__: None
+
+    NotImplemented: _NotImplementedType
+
 @disjoint_base
 class BaseException:
     args: tuple[Any, ...]

stdlib/types.pyi

@@ -717,9 +717,9 @@ if sys.version_info >= (3, 10):
     @final
     class EllipsisType: ...
 
-    from builtins import _NotImplementedType
+    @final
+    class NotImplementedType(Any): ...
 
-    NotImplementedType = _NotImplementedType
     @final
     class UnionType:
         @property