`asyncio.Timeout.__aexit__` does not handle `BaseExceptionGroup`

[PLPeeters]

Bug report

Bug description:

There may be a good reason for this I am not seeing, but in the asyncio.Timeout.__aexit__ handler, the exception group handling seems too narrow:

cpython/Lib/asyncio/timeouts.py

Lines 113 to 119 in 9743d06

	if issubclass(exc_type, exceptions.CancelledError):
	raise TimeoutError from exc_val
	elif exc_val is not None:
	self._insert_timeout_error(exc_val)
	if isinstance(exc_val, ExceptionGroup):
	for exc in exc_val.exceptions:
	self._insert_timeout_error(exc)

Given exc_val itself can be a BaseException and _insert_timeout_error takes a BaseException as an argument, I fail to see a reason not to check for superclass BaseExceptionGroup instead.

cpython/Lib/asyncio/timeouts.py

Line 133 in 9743d06

def _insert_timeout_error(exc_val: BaseException) -> None:

This no longer impacts me as I implemented what I was aiming for in a better way, but it still looks like a bug. Is it?

CPython versions tested on:

3.13

Operating systems tested on:

Linux