PEP673 Self type not working

[remdragon]

Bug Report

New PEP 673 Self doesn't seem to work as advertised.

To Reproduce

The following example was adapted from https://docs.python.org/3/whatsnew/3.11.html#whatsnew311-pep673

from typing import Self

class MyLock:
	def __enter__(self) -> Self:
		self.lock()
		return self
	
	def lock( self ) -> None: ...

class MyInt:
	def __init__( self, value: int ) -> None: ...
	
	@classmethod
	def fromhex(cls, s: str) -> Self:
		return cls(int(s, 16))

Also reproduced here:
https://mypy-play.net/?mypy=latest&python=3.11&gist=234463d18e41111a70ac5276325334f7

Expected Behavior

Self should be a placeholder for TypeVar(...)

Actual Behavior

self_test.py:4: error: Variable "typing.Self" is not valid as a type [valid-type]
self_test.py:4: note: See https://mypy.readthedocs.io/en/stable/common_issues.html#variables-vs-type-aliases
self_test.py:14: error: Variable "typing.Self" is not valid as a type [valid-type]
self_test.py:14: note: See https://mypy.readthedocs.io/en/stable/common_issues.html#variables-vs-type-aliases

Your Environment

mypy --python-version 3.11 --strict --implicit-reexport --disallow-untyped-defs

Windows 10 Pro 21H2
Python 3.11.0 (main, Oct 24 2022, 18:13:38) [MSC v.1933 32 bit (Intel)] on win32
accept-types==0.4.1
aiofiles==22.1.0
aiohttp==3.8.3
aioshutil==1.2
aiosignal==1.2.0
altgraph==0.17.3
async-timeout==4.0.2
attrs==22.1.0
bbcode==1.1.0
bcrypt==4.0.1
boto3==1.26.8
botocore==1.29.8
cachelib==0.9.0
certifi==2022.9.24
cffi==1.15.1
chardet==5.0.0
charset-normalizer==2.1.1
click==8.1.3
colorama==0.4.6
coverage==6.5.0
cryptography==38.0.1
dnspython==2.2.1
et-xmlfile==1.1.0
Flask==2.2.2
Flask-Login==0.6.2
Flask-Session==0.4.0
fpdf==1.7.2
frozenlist==1.3.1
future==0.18.2
gevent==22.10.2
greenlet==2.0.0
idna==3.4
install==1.3.5
itsdangerous==2.1.2
Jinja2==3.1.2
jmespath==1.0.1
lark==1.1.4
MarkupSafe==2.1.1
multidict==6.0.2
mypy==0.991
mypy-extensions==0.4.3
names==0.3.0
natural==0.2.0
netaddr==0.8.0
openpyxl==3.0.10
paramiko==2.11.0
pefile==2022.5.30
Pillow==9.2.0
psutil==5.9.3
psycopg2 @ file:///C:/users/royce3/Downloads/psycopg2-2.9.3-cp311-cp311-win32.whl
pyasn1==0.4.8
pyasn1-modules==0.2.8
pycparser==2.21
pycryptodomex==3.15.0
pydub==0.25.1
pyinstaller==5.6
pyinstaller-hooks-contrib==2022.10
pyinstrument==4.3.0
PyMySQL==1.0.2
PyNaCl==1.5.0
pyodbc==4.0.34
pyOpenSSL==22.1.0
python-dateutil==2.8.2
python-ldap @ file:///C:/users/royce3/Downloads/python_ldap-3.4.0-cp311-cp311-win32.whl
python-pam==2.0.2
pytz==2022.6
pytz-deprecation-shim==0.1.0.post0
pyvmomi==7.0.3
pywin32==304
pywin32-ctypes==0.2.0
pyzipper==0.3.6
reportlab==3.6.11
requests==2.28.1
s3transfer==0.6.0
service-identity==21.1.0
six==1.16.0
termcolor==2.0.1
tornado==6.2
tornroutes==0.5.1
types-aiofiles==22.1.0.3
types-certifi==2021.10.8.3
types-click==7.1.8
types-cryptography==3.3.23.1
types-Flask==1.1.6
types-Jinja2==2.11.9
types-MarkupSafe==1.1.10
types-paramiko==2.11.6
types-PyMySQL==1.0.19.1
types-pyOpenSSL==22.1.0.2
types-python-dateutil==2.8.19.2
types-pytz==2022.5.0.0
types-pyvmomi==7.0.8.2
types-requests==2.28.11.2
types-setuptools==65.5.0.2
types-six==1.16.21.1
types-termcolor==1.1.6
types-tornado==5.1.1
types-tzlocal==4.2.2.2
types-urllib3==1.26.25.1
types-Werkzeug==1.0.9
typing_extensions==4.4.0
tzdata==2022.5
tzlocal==4.2
urllib3==1.26.12
Werkzeug==2.2.2
wsman==0.9.27
XlsxWriter==3.0.3
yarl==1.8.1
zope.event==4.5.0
zope.interface==5.5.0

[AlexWaygood]

PEP 673 isn't supported by mypy yet, but will be supported in the next release.

[AlexWaygood]

See #14041. In the meantime, you can use a TypeVar:

from typing import TypeVar

Self = TypeVar("Self")

class MyLock:
	def __enter__(self: Self) -> Self:
		self.lock()
		return self
	
	def lock( self ) -> None: ...

class MyInt:
	def __init__( self, value: int ) -> None: ...
	
	@classmethod
	def fromhex(cls: type[Self], s: str) -> Self:
		return cls(int(s, 16))