Mark stub-only types with an underscore

stdlib/2/sys.pyi

@@ -7,8 +7,8 @@ from typing import (
 from types import FrameType, ModuleType, TracebackType, ClassType
 
 # The following type alias are stub-only and do not exist during runtime
-ExcInfo = Tuple[Type[BaseException], BaseException, TracebackType]
-OptExcInfo = Tuple[Optional[Type[BaseException]], Optional[BaseException], Optional[TracebackType]]
+_ExcInfo = Tuple[Type[BaseException], BaseException, TracebackType]
+_OptExcInfo = Tuple[Optional[Type[BaseException]], Optional[BaseException], Optional[TracebackType]]
 
 class _flags:
     bytes_warning = ...  # type: int
@@ -117,7 +117,7 @@ def __excepthook__(type_: type, value: BaseException, traceback: TracebackType)
 def exc_clear() -> None:
     raise DeprecationWarning()
 # TODO should be a union of tuple, see mypy#1178
-def exc_info() -> OptExcInfo: ...
+def exc_info() -> _OptExcInfo: ...
 
 # sys.exit() accepts an optional argument of anything printable
 def exit(arg: Any = ...) -> NoReturn:

stdlib/2and3/wsgiref/types.pyi

@@ -15,11 +15,11 @@
 # you need to use 'WSGIApplication' and not simply WSGIApplication when type
 # hinting your code.  Otherwise Python will raise NameErrors.
 
-from sys import OptExcInfo
+from sys import _OptExcInfo
 from typing import Callable, Dict, Iterable, List, Any, Text, Protocol, Tuple, Optional
 
 class StartResponse(Protocol):
-    def __call__(self, status: str, headers: List[Tuple[str, str]], exc_info: Optional[OptExcInfo] = ...) -> Callable[[bytes], Any]: ...
+    def __call__(self, status: str, headers: List[Tuple[str, str]], exc_info: Optional[_OptExcInfo] = ...) -> Callable[[bytes], Any]: ...
 
 WSGIEnvironment = Dict[Text, Any]
 WSGIApplication = Callable[[WSGIEnvironment, StartResponse], Iterable[bytes]]

stdlib/3/sys.pyi

@@ -15,8 +15,8 @@ from importlib.abc import MetaPathFinder
 _T = TypeVar('_T')
 
 # The following type alias are stub-only and do not exist during runtime
-ExcInfo = Tuple[Type[BaseException], BaseException, TracebackType]
-OptExcInfo = Tuple[Optional[Type[BaseException]], Optional[BaseException], Optional[TracebackType]]
+_ExcInfo = Tuple[Type[BaseException], BaseException, TracebackType]
+_OptExcInfo = Tuple[Optional[Type[BaseException]], Optional[BaseException], Optional[TracebackType]]
 
 # ----- sys variables -----
 abiflags: str
@@ -132,7 +132,7 @@ def _current_frames() -> Dict[int, Any]: ...
 def displayhook(value: Optional[int]) -> None: ...
 def excepthook(type_: Type[BaseException], value: BaseException,
                traceback: TracebackType) -> None: ...
-def exc_info() -> OptExcInfo: ...
+def exc_info() -> _OptExcInfo: ...
 # sys.exit() accepts an optional argument of anything printable
 def exit(arg: object = ...) -> NoReturn:
     raise SystemExit()