mypy_extensions: fix TypeVar usage (#7937)

#7928

Author: AlexWaygood

stubs/mypy-extensions/mypy_extensions.pyi

@@ -1,7 +1,7 @@
 import abc
 from _typeshed import Self
 from collections.abc import Callable, ItemsView, KeysView, Mapping, ValuesView
-from typing import Any, Generic, TypeVar
+from typing import Any, Generic, TypeVar, overload
 
 _T = TypeVar("_T")
 _U = TypeVar("_U")
@@ -21,12 +21,30 @@ class _TypedDict(Mapping[str, object], metaclass=abc.ABCMeta):
     def __delitem__(self, k: NoReturn) -> None: ...
 
 def TypedDict(typename: str, fields: dict[str, type[Any]], total: bool = ...) -> type[dict[str, Any]]: ...
-def Arg(type: _T = ..., name: str | None = ...) -> _T: ...
-def DefaultArg(type: _T = ..., name: str | None = ...) -> _T: ...
-def NamedArg(type: _T = ..., name: str | None = ...) -> _T: ...
-def DefaultNamedArg(type: _T = ..., name: str | None = ...) -> _T: ...
-def VarArg(type: _T = ...) -> _T: ...
-def KwArg(type: _T = ...) -> _T: ...
+@overload
+def Arg(type: _T, name: str | None = ...) -> _T: ...
+@overload
+def Arg(*, name: str | None = ...) -> Any: ...
+@overload
+def DefaultArg(type: _T, name: str | None = ...) -> _T: ...
+@overload
+def DefaultArg(*, name: str | None = ...) -> Any: ...
+@overload
+def NamedArg(type: _T, name: str | None = ...) -> _T: ...
+@overload
+def NamedArg(*, name: str | None = ...) -> Any: ...
+@overload
+def DefaultNamedArg(type: _T, name: str | None = ...) -> _T: ...
+@overload
+def DefaultNamedArg(*, name: str | None = ...) -> Any: ...
+@overload
+def VarArg(type: _T) -> _T: ...
+@overload
+def VarArg() -> Any: ...
+@overload
+def KwArg(type: _T) -> _T: ...
+@overload
+def KwArg() -> Any: ...
 
 # Return type that indicates a function does not return.
 # Deprecated: Use typing.NoReturn instead.