Doing variable: typing.Optional[typing.Self] = self will fail

[McDic]

Bug Report

If you do variable: typing.Optional[typing.Self] = self in method of your class, you will get a mypy error.

To Reproduce

import typing

class TestClass:
    def __init__(self, parent: typing.Optional[typing.Self]) -> None:
        self.parent = parent

    def get_depth(self) -> int:
        current: typing.Optional[typing.Self] = self
        iteration = 0
        while current is not None:
            iteration += 1
            current = current.parent
        return iteration - 1

Expected Behavior

There should be no error.

Actual Behavior

You will get following error on current = self part.

error: Incompatible types in assignment (expression has type "TestClass", variable has type "Self | None")  [assignment]

Your Environment

• Mypy version used: 1.6.1
• Mypy command-line flags: mypy (filename)
• Mypy configuration options from mypy.ini (and other config files): Nothing
• Python version used: 3.11.6

[ilevkivskyi]

This is duplicate of #14075