False negative when declaring a class with a literal string base, which could refer to a forward-reference type alias

Bug Report

mypy interprets a literal string, which could refer to a forward-reference type alias, as a valid class base.

To Reproduce

The following example uses both a forward reference (class B1("A")) and a string which doesn't refer to anything (class B2("D")):

class B1("A"):
    pass

b1: B1 = B1()
b1.a = ""  # mypy: Incompatible types in assignment (expression has type "str", variable has type "int") [assignment]

class B2("D"):  # mypy: Class cannot subclass value of type "Any" [misc] \           
                # mypy: Name "D" is not defined [name-defined]
    pass

class A:
    a: int

Expected Behavior

I expect the following snippet to show up if we're not under a typing.TYPE_CHECKING block:

class B1("A"):  # mypy: Invalid base class "A" [misc] \
                # mypy: See https://mypy.readthedocs.io/en/stable/common_issues.html#variables-vs-type-aliases \
                # mypy: Variable "A" is not valid as a type [valid-type]
    pass

EDIT: this is a more sensible expected error:

class B1("A"):  # mypy: Invalid base class [misc]
    pass

I can't gauge from PEP 613 whether or not this should should be OK (mypy doesn't show any errors, but FWIW pylance or pyright sees this as an error):

from __future__ import annotations
from typing import TYPE_CHECKING

if TYPE_CHECKING:
    class B("A"):  # pylance: Expected class type but received "Literal['A']" \
                   # pylance: Base class type is unknown, obscuring type of derived class
        pass

class A:
    pass

Your Environment

Tested on mypy-play.net:

• Mypy version used: 0.981 and master
• Mypy command-line flags: None
• Mypy configuration options from mypy.ini (and other config files): show_error_codes = True
• Python version used: 3.10

Beginne damit, die beiden Beispiele für Klassenbasen auf mypy-play.net mit mypy 0.981 oder master und ohne Befehlszeilen-Flags nachzustellen. Vergleiche die Diagnosen für die Vorwärtsreferenz und die nicht auflösbaren Literal-String-Basen und ermittle dann das beabsichtigte Verhalten außerhalb und innerhalb von TYPE_CHECKING; fertig ist es, wenn die relevanten Fälle den vereinbarten Fehler für eine ungültige Basis melden, ohne gültige Vorwärtsreferenzen zu beeinträchtigen.