mark some positional-only arguments (#4693)

https://github.com/python/mypy/pull/9626 will make stubtest a little bit
stricter about positional-only arguments for dunders like __init__

Co-authored-by: hauntsaninja <>

stdlib/3/collections/__init__.pyi

@@ -74,7 +74,7 @@ else:
 
 class UserDict(MutableMapping[_KT, _VT]):
     data: Dict[_KT, _VT]
-    def __init__(self, dict: Optional[Mapping[_KT, _VT]] = ..., **kwargs: _VT) -> None: ...
+    def __init__(self, __dict: Optional[Mapping[_KT, _VT]] = ..., **kwargs: _VT) -> None: ...
     def __len__(self) -> int: ...
     def __getitem__(self, key: _KT) -> _VT: ...
     def __setitem__(self, key: _KT, item: _VT) -> None: ...

stdlib/3/functools.pyi

@@ -77,9 +77,9 @@ class partialmethod(Generic[_T]):
     args: Tuple[Any, ...]
     keywords: Dict[str, Any]
     @overload
-    def __init__(self, func: Callable[..., _T], *args: Any, **keywords: Any) -> None: ...
+    def __init__(self, __func: Callable[..., _T], *args: Any, **keywords: Any) -> None: ...
     @overload
-    def __init__(self, func: _Descriptor, *args: Any, **keywords: Any) -> None: ...
+    def __init__(self, __func: _Descriptor, *args: Any, **keywords: Any) -> None: ...
     def __get__(self, obj: Any, cls: Type[Any]) -> Callable[..., _T]: ...
     @property
     def __isabstractmethod__(self) -> bool: ...

stdlib/3/unittest/mock.pyi

@@ -73,7 +73,7 @@ class Base:
     def __init__(self, *args: Any, **kwargs: Any) -> None: ...
 
 class NonCallableMock(Base, Any):  # type: ignore
-    def __new__(cls, *args: Any, **kw: Any) -> NonCallableMock: ...
+    def __new__(__cls, *args: Any, **kw: Any) -> NonCallableMock: ...
     def __init__(
         self,
         spec: Union[List[str], object, Type[object], None] = ...,