`types.GeneratorType.gi_frame` should be `FrameType | None`

[x42005e1f]

typeshed/stdlib/types.pyi

Lines 402 to 403 in 7fde970

	@property
	def gi_frame(self) -> FrameType: ...

This issue is similar to #14780. The gi_frame property becomes None when the generator iterator completes:

>>> def generator_function():
... return
... yield
>>> gen = generator_function()
>>> gen.gi_frame
<frame at 0x7f2ebe641620, file '<stdin>', line 1, code generator_function>
>>> next(gen) # consume
Traceback (most recent call last):
 File "<stdin>", line 1, in <module>
StopIteration
>>> gen.gi_frame is None
True

The same applies to AsyncGeneratorType.ag_frame:

>>> async def asyncgen_function():
... return
... yield
>>> asyncgen = asyncgen_function()
>>> asyncgen.ag_frame
<frame at 0x7f37cf7d5c60, file '<stdin>', line 1, code asyncgen_function>
>>> [*asyncgen.asend(None).__await__()] # consume
Traceback (most recent call last):
 File "<stdin>", line 1, in <module>
StopAsyncIteration
>>> asyncgen.ag_frame is None
True

Notably, this was mentioned in both the linked issue and python/cpython#112428 (Python 3.12.1), to which it refers, but was ignored in the PR (#14802), meaning the issue was closed prematurely (why?). Moreover, none of the *_frame properties actually depend on the Python version. 3.12.0 introduced a regression, as mentioned in python/cpython#111058. The above examples (and a similar one for coroutine objects) can be easily reproduced even on Python 3.6:

Python 3.6.15 (default, Apr 25 2022, 01:55:53) 
[GCC 9.4.0] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> async def coroutine_function():
... pass
>>> coro = coroutine_function()
>>> coro.cr_frame
<frame object at 0x7fe26e728a08>
>>> coro.send(None) # consume
Traceback (most recent call last):
 File "<stdin>", line 1, in <module>
StopIteration
>>> coro.cr_frame is None
True

[AlexWaygood]

Thanks! PR welcome :-)