typing: type decorators so they don't count as untyped lines (#5348)

stdlib/typing.pyi

@@ -12,7 +12,6 @@ if sys.version_info >= (3, 9):
 # Definitions of special type checking related constructs.  Their definitions
 # are not used, so their value does not matter.
 
-overload = object()
 Any = object()
 
 class TypeVar:
@@ -35,6 +34,10 @@ _promote = object()
 class _SpecialForm:
     def __getitem__(self, typeargs: Any) -> object: ...
 
+_F = TypeVar("_F", bound=Callable[..., Any])
+
+def overload(func: _F) -> _F: ...
+
 Union: _SpecialForm = ...
 Optional: _SpecialForm = ...
 Tuple: _SpecialForm = ...
@@ -46,7 +49,6 @@ Type: _SpecialForm = ...
 ClassVar: _SpecialForm = ...
 if sys.version_info >= (3, 8):
     Final: _SpecialForm = ...
-    _F = TypeVar("_F", bound=Callable[..., Any])
     def final(f: _F) -> _F: ...
     Literal: _SpecialForm = ...
     # TypedDict is a (non-subscriptable) special form.
@@ -94,11 +96,9 @@ _KT_co = TypeVar("_KT_co", covariant=True)  # Key type covariant containers.
 _VT_co = TypeVar("_VT_co", covariant=True)  # Value type covariant containers.
 _T_contra = TypeVar("_T_contra", contravariant=True)  # Ditto contravariant.
 _TC = TypeVar("_TC", bound=Type[object])
-_C = TypeVar("_C", bound=Callable[..., Any])
 
-no_type_check = object()
-
-def no_type_check_decorator(decorator: _C) -> _C: ...
+def no_type_check(arg: _F) -> _F: ...
+def no_type_check_decorator(decorator: _F) -> _F: ...
 
 # Type aliases and type constructors
 
@@ -681,7 +681,7 @@ class _TypedDict(Mapping[str, object], metaclass=ABCMeta):
 def NewType(name: str, tp: Type[_T]) -> Type[_T]: ...
 
 # This itself is only available during type checking
-def type_check_only(func_or_cls: _C) -> _C: ...
+def type_check_only(func_or_cls: _F) -> _F: ...
 
 if sys.version_info >= (3, 7):
     from types import CodeType