What's wrong

In Python 3.7+ a class __aiter__ must return an async iterator object (an object that implements __anext__). An async generator (an async function with yield) is considered an async iterator object.

The following is valid and should not be flagged as an incorrect async definition.

class Ex(object):
    async def __aiter__(self):
        count = 0
        while count < 50:
            count += 1
            yield count

The following is invalid and should be flagged as incorrect (it'll also throw a type error or somesuch if actually used in async for).

class Ex(object):
    async def __aiter__(self):
        count = 0
        while count < 50:
            count += 1

How it should be

See above. Don't throw an error.

Flake8 version and plugins

{
"dependencies": [],
"platform": {
"python_implementation": "CPython",
"python_version": "3.8.10",
"system": "Linux"
},
"plugins": [
{
"is_local": false,
"plugin": "flake8-bandit",
"version": "3.0.0"
},
{
"is_local": false,
"plugin": "flake8-broken-line",
"version": "0.4.0"
},
{
"is_local": false,
"plugin": "flake8-bugbear",
"version": "22.3.23"
},
{
"is_local": false,
"plugin": "flake8-class-attributes-order",
"version": "0.1.3"
},
{
"is_local": false,
"plugin": "flake8-comprehensions",
"version": "3.8.0"
},
{
"is_local": false,
"plugin": "flake8-darglint",
"version": "1.8.1"
},
{
"is_local": false,
"plugin": "flake8-debugger",
"version": "4.0.0"
},
{
"is_local": false,
"plugin": "flake8-docstrings",
"version": "1.6.0, pydocstyle: 6.1.1"
},
{
"is_local": false,
"plugin": "flake8-eradicate",
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},
{
"is_local": false,
"plugin": "flake8-string-format",
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{
"is_local": false,
"plugin": "flake8_commas",
"version": "2.1.0"
},
{
"is_local": false,
"plugin": "flake8_isort",
"version": "4.1.1"
},
{
"is_local": false,
"plugin": "flake8_quotes",
"version": "3.3.1"
},
{
"is_local": false,
"plugin": "mccabe",
"version": "0.6.1"
},
{
"is_local": false,
"plugin": "naming",
"version": "0.12.1"
},
{
"is_local": false,
"plugin": "pycodestyle",
"version": "2.8.0"
},
{
"is_local": false,
"plugin": "pyflakes",
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},
{
"is_local": false,
"plugin": "pylint",
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{
"is_local": false,
"plugin": "rst-docstrings",
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},
{
"is_local": false,
"plugin": "wemake_python_styleguide",
"version": "0.16.1"
}
],
"version": "4.0.1"
}

pip information

adblockparser==0.7
amkv==0.1.2
anyio==3.5.0
appdirs==1.4.3
apturl==0.5.2
astor==0.8.1
async-generator==1.10
async-timeout==4.0.2
asyncache==0.1.1
atomicwrites==1.1.5
attrs==19.3.0
Automat==0.8.0
bandit==1.7.4
bcrypt==3.1.7
beautifulsoup4==4.11.1
blinker==1.4
Brlapi==0.7.0
Brotli==1.0.9
cachetools==5.0.0
certifi==2019.11.28
cffi==1.14.0
chardet==4.0.0
charset-normalizer==2.0.12
Click==7.0
colorama==0.4.3
command-not-found==0.3
constantly==15.1.0
crit==0.0.1
croniter==1.3.4
cryptography==2.8
cupshelpers==1.0
cycler==0.10.0
Cython==0.29.14
darglint==1.8.1
dblatex===0.3.11py3
dbus-python==1.2.16
decorator==4.4.2
defer==1.0.6
Deprecated==1.2.13
distlib==0.3.0
distro==1.4.0
distro-info===0.23ubuntu1
dnspython==1.16.0
docutils==0.18.1
EditorConfig==0.12.2
entrypoints==0.3
eradicate==2.1.0
et-xmlfile==1.0.1
fasteners==0.14.1
ffmpeg-normalize==1.22.9
ffmpeg-progress-yield==0.2.0
filelock==3.0.12
flake8==4.0.1
flake8-bandit==3.0.0
flake8-broken-line==0.4.0
flake8-bugbear==22.3.23
flake8-class-attributes-order==0.1.3
flake8-commas==2.1.0
flake8-comprehensions==3.8.0
flake8-debugger==4.0.0
flake8-docstrings==1.6.0
flake8-eradicate==1.2.0
flake8-isort==4.1.1
flake8-polyfill==1.0.2
flake8-quotes==3.3.1
flake8-rst-docstrings==0.2.5
flake8-string-format==0.3.0
flakeheaven==0.11.1
funcparserlib==0.3.6
future==0.18.2
gevent==21.12.0
gil-load==0.4.2
gitdb==4.0.9
gitdb2==2.0.6
GitPython==3.1.27
gpg===1.13.1-unknown
graphviz==0.16
greenlet==1.1.2
gssapi==1.6.1
h11==0.12.0
h2==4.1.0
h5py==2.10.0
hpack==4.0.0
html5-parser==0.4.10
html5lib==1.0.1
httpcore==0.14.7
httplib2==0.14.0
httpx==0.22.0
hypercorn==0.13.2
hyperframe==6.0.1
hyperlink==19.0.0
idna==2.8
imageio==2.4.1
importlib-metadata==1.5.0
incremental==21.3.0
iotop==0.6
isc==2.0
isort==5.10.1
jdcal==1.0
Jinja2==2.10.1
jsbeautifier==1.10.3
Keras==2.2.4
Keras-Applications==1.0.6
Keras-Preprocessing==1.0.5
keyring==18.0.1
kiwisolver==1.0.1
language-selector==0.1
launchpadlib==1.10.13
lazr.restfulclient==0.14.2
lazr.uri==1.0.3
linecache2==1.0.0
lockfile==0.12.2
louis==3.12.0
lxml==4.5.0
macaroonbakery==1.3.1
Mako==1.1.0
Markdown==3.1.1
MarkupSafe==1.1.0
matplotlib==3.1.2
mccabe==0.6.1
memory-analyzer==0.1.2
meson==0.53.2
mock==3.0.5
monotonic==1.5
more-itertools==4.2.0
mpi4py==3.0.3
msgpack==0.6.2
multidict==6.0.2
mutagen==1.45.1
nest-asyncio==1.5.5
netaddr==0.7.19
netifaces==0.10.4
networkx==2.8
nftables==0.1
nose==1.3.7
numexpr==2.7.1
numpy==1.22.3
oauthlib==3.1.0
objgraph==3.5.0
olefile==0.46
opencv-python==4.5.5.64
openpyxl==3.0.3
outcome==1.1.0
packaging==21.3
pandas==0.25.3
parameterized==0.7.0
paramiko==2.6.0
patsy==0.5.1
pbr==5.4.5
peewee==3.14.10
pep8-naming==0.12.1
pexpect==4.6.0
Pillow==7.0.0
pluggy==0.13.0
ply==3.11
prettytable==2.1.0
priority==1.3.0
protobuf==3.6.1
psutil==5.5.1
py==1.8.1
pyasn1==0.4.2
pyasn1-modules==0.2.1
pycairo==1.16.2
pycodestyle==2.8.0
pycparser==2.19
pycrypto==2.6.1
pycryptodomex==3.14.1
pycups==1.9.73
pydocstyle==6.1.1
pydot==1.4.1
pyflakes==2.4.0
Pygments==2.11.2
PyGObject==3.36.0
pygpu==0.7.6
PyHamcrest==1.9.0
PyJWT==1.7.1
pymacaroons==0.13.0
Pympler==0.9
PyNaCl==1.3.0
pyOpenSSL==19.0.0
pyparsing==3.0.8
PyQt5==5.14.1
PyQtWebEngine==5.14.0
pyRFC3339==1.1
pytest==4.6.9
python-apt==2.0.0+ubuntu0.20.4.6
python-augeas==0.5.0
python-dateutil==2.7.3
python-debian===0.1.36ubuntu1
python-ldap==3.2.0
python-libtorrent==1.1.13
python-multipart==0.0.5
python-yubico==1.3.3
pytz==2019.3
pyusb==1.0.2
PyWavelets==1.3.0
pyxdg==0.26
PyYAML==5.3.1
pyzmq==18.1.1
qrtools==2.0
qt5reactor==0.6
QtPy==1.9.0
redis==4.2.2
reportlab==3.5.34
requests==2.27.1
requests-unixsocket==0.2.0
restructuredtext-lint==1.4.0
rfc3986==1.3.2
salt==3000.2
scikit-image==0.19.2
scipy==1.8.0
seaborn==0.10.0
SecretStorage==2.3.1
selinux==3.0
service-identity==18.1.0
simplejson==3.16.0
sip==4.19.21
six==1.14.0
slip==0.6.5
slip.dbus==0.6.5
smmap==5.0.0
smmap2==2.0.5
sniffio==1.1.0
snowballstemmer==2.0.0
sortedcontainers==2.1.0
soupsieve==1.9.5
splash==3.5
ssh-import-id==5.10
starlette==0.19.0
stevedore==1.32.0
systemd-python==234
tables==3.6.1
testfixtures==6.10.1
testresources==2.0.0
Theano==1.0.4
tifffile==2022.4.8
toml==0.10.0
tqdm==4.64.0
traceback2==1.4.0
trio==0.20.0
Twisted==22.4.0
typing-extensions==4.2.0
ubuntu-advantage-tools==27.4
ubuntu-drivers-common==0.0.0
unattended-upgrades==0.1
unittest2==1.1.0
urllib3==1.26.9
usb-creator==0.3.7
virtualenv==20.0.17
wadllib==1.3.3
wcwidth==0.1.8
webencodings==0.5.1
websockets==10.3
wemake-python-styleguide==0.16.1
Werkzeug==2.1.1
wrapt==1.14.0
wsproto==1.1.0
xdis==6.0.3
xkit==0.0.0
xlrd==1.1.0
xlwt==1.3.0
xvfbwrapper==0.2.9
yarl==1.7.2
youtube-dl==2021.12.17
yt-dlp==2022.4.8
zipp==1.0.0
zope.event==4.5.0
zope.interface==4.7.1

OS information

Ubuntu 20.04