mypy doesn't understand partial unpacking with star arguments

Bug Report

While working on https://github.com/qutebrowser/qutebrowser/pull/5317 I think I may have found a bug in mypy. The following code looks correct, and runs fine on my machine.

To Reproduce

1. Save the following code to file /tmp/reproducer.py

#!/usr/bin/env python
# -*- coding: utf-8 -*-
# vim: fenc=utf-8:et:ts=4:sts=4:sw=4:fdm=marker
from typing import Optional, Sequence, Mapping
import collections

class ModuleInfo:
    def __init__(
        self,
        name: str,
        version_attributes: Sequence[str],
        min_version: Optional[str] = None
    ):
        self.name = name
        self._version_attributes = version_attributes
        self.min_version = min_version

MODULE_INFO: Mapping[str, ModuleInfo] = collections.OrderedDict([
    (name, ModuleInfo(name, *args))
    for (name, *args) in
    [
        ('sip', ['SIP_VERSION_STR']),
        ('colorama', ['VERSION', '__version__']),
        ('pypeg2', ['__version__']),
        ('jinja2', ['__version__']),
        ('pygments', ['__version__']),
        ('yaml', ['__version__']),
        ('adblock', ['__version__'], "0.3.2"),
        ('cssutils', ['__version__']),
        ('attr', ['__version__']),
        ('PyQt5.QtWebEngineWidgets', []),
        ('PyQt5.QtWebEngine', ['PYQT_WEBENGINE_VERSION_STR']),
        ('PyQt5.QtWebKitWidgets', []),
    ]
])

2. Run mypy /tmp/reproducer.py.

Expected Behavior

There should be no type errors.

Actual Behavior

The output of the command in step 2 returns:

reproducer.py:19: error: List comprehension has incompatible type List[Tuple[Sequence[str], ModuleInfo]]; expected List[Tuple[str, ModuleInfo]]
reproducer.py:19: error: Argument 1 to "ModuleInfo" has incompatible type "Sequence[str]"; expected "str"
reproducer.py:19: error: Argument 2 to "ModuleInfo" has incompatible type "*List[Sequence[str]]"; expected "Optional[str]"
Found 3 errors in 1 file (checked 1 source file)

Your Environment

• Mypy version used: mypy 0.790
• Mypy command-line flags: mypy /tmp/reproducer.py
• Mypy configuration options from mypy.ini (and other config files): None, I think
• Python version used: Python 3.8.6
• Operating system and version: Gentoo Linux

Commencez par l’exemple /tmp/reproducer.py et exécutez mypy /tmp/reproducer.py avec les versions de Python et de mypy indiquées. Suivez la manière dont le vérificateur de types traite le déballage d’un tuple avec astérisque et l’appel du constructeur, puis mettez à jour le comportement afin que le reproducer ne signale aucune erreur de typage.