Variable can be annotated with Final and ClassVar at the same time #10477

Bug Report

Variable can be annotated with Final and ClassVar at the same time.

But PEP 591 says that this is forbidden:

Variables should not be annotated with both ClassVar and Final.

To Reproduce

1. Declarate class variable with both Final and ClassVar annotations.

from typing_extensions import Final, ClassVar


class Foo:
    a: Final[ClassVar[int]] = 10

Expected Behavior

mypy should fail.

error: Variable should not be annotated with both ClassVar and Final

Actual Behavior

mypy do not raise any error.

Success: no issues found in 1 source file

Your Environment

• Mypy version used: 0.812
• Mypy configuration options from mypy.ini (and other config files):
• Python version used: 3.6.8
• Operating system and version: macOS Big Sur 11.2.1