Mypy should warn when comparing lists that hold a union of incomparable types

Feature

As of mypy 0.991 on Python 3.11.0, mypy --strict doesn't report any problems on this code:

from typing import List, Union
a: List[Union[int, str]] = ['a']
b: List[Union[int, str]] = [1]
result = a < b

Despite mypy passing, actually running this results in TypeError: '<' not supported between instances of 'str' and 'int'. I think ideally mypy would catch this.

Pitch

While the problem was much less obvious, this affected a real project at https://github.com/certbot/certbot/issues/9481 so I think it'd be useful if mypy could help stop bugs like this from slipping through.

My knowledge of mypy and especially its internals is pretty limited, but is there a sane way to do this? Would it be possible to do something like write the annotation of list.__lt__ in the typeshed so it only accepts another list whose elements are of a type that can be compared with its own?

Beginne damit, das gemeldete Python 3.11-Beispiel mit mypy --strict zu reproduzieren, und bestätige den Laufzeit-TypeError. Untersuche, wie list.lt typisiert ist und ob typeshed vergleichbare Elementtypen ausdrücken kann. Als abgeschlossen gilt die Aufgabe, wenn mypy den unsicheren Vergleich meldet, ohne gültige Vergleiche von vergleichbaren Listen abzulehnen.