Crash on type alias bounded by and defaulted to itself

[MeGaGiGaGon]

Crash Report

Found while messing around.

Traceback

Collapsed for readability

Deferral trace:
    __main__:1
    __main__:1
    __main__:1
    __main__:-1
    __main__:1
    __main__:1
    __main__:1
    __main__:1
    __main__:-1
    __main__:1
    __main__:1
    __main__:1
    __main__:1
    __main__:1
    __main__:1
    __main__:1
    __main__:1
    __main__:1
    __main__:1
    __main__:1
    __main__:1
    __main__:1
    __main__:1
    __main__:1
    __main__:1
    __main__:1
    __main__:1
    __main__:1
<string>: error: INTERNAL ERROR: maximum semantic analysis iteration count reached

To Reproduce

https://mypy-play.net/?mypy=master&python=3.14&gist=20fd30ebe61db2c71150e54a6c86a1bb

type A[T: A = A] = int

PS > uvx mypy@https://github.com/python/mypy.git --show-traceback -c 'type A[T: A = A] = int'

Your Environment

• Mypy version used: Current master
• Mypy command-line flags: --show-traceback -c "code"
• Mypy configuration options from mypy.ini (and other config files): None
• Python version used: 3.14? Whatever uvx does.
• Operating system and version: Windows 11

[ilevkivskyi]

This is not specific to the new syntax, old style variant of this crashes as well, however with a different error:

from typing import TypeVar

T = TypeVar("T", default=A)

A = list[T]

[ilevkivskyi]

Also I am tempted to mark this as a duplicate of #17716, but that one is specific to generic class, while this one is specific to a generic alias, so let's keep both open for now.

Also @brianschubert I wold propose to use PEP 695 label only for issues that only happen with the new syntax (I removed the label from the other two issues as well).