[Python 3.9] Mypy complains str has no attribute removesuffix

[fniessink]

Bug Report

Mypy complains str has no attribute removesuffix with Python 3.9.

To Reproduce

python3.9 -m venv venv
. venv/bin/activate
pip install mypy
echo '"123".removesuffix("3")' > test.py
mypy test.py

Expected Output

Success: no issues found in 1 source file

Actual Output

test.py:1: error: "str" has no attribute "removesuffix"
Found 1 error in 1 file (checked 1 source file)

Your Environment

• Mypy version used: 0.782
• Mypy command-line flags: none
• Mypy configuration options from mypy.ini (and other config files): none
• Python version used: 3.9.0
• Operating system and version: macOS Catalina, version 10.15.7

[hauntsaninja]

I added this in typeshed a couple months ago / is fixed on master

[hauntsaninja]

Thank you for the report, though! :-)

[fniessink]

No problem. However, I'm not sure what's next. I checked the mypy documentation and FAQ but it isn't clear to me what I'm supposed to do to get mypy correctly checking Python 3.9 code?

[hauntsaninja]

You can install mypy from Github master or wait for the next release (#9290). Or you can continue to use mypy 0.782, download a copy of the latest typeshed and use mypy --custom-typeshed-dir <location of downloaded typeshed>.

(Based on your report this doesn't apply, but if the Python you're using to run mypy is older, you'll need to pass in --python-version 3.9, as per https://mypy.readthedocs.io/en/stable/command_line.html#cmdoption-mypy-python-version)