segfault on recursive generic function class

Crash Report

Seg fault

Traceback

$ mypy . --show-traceback
Segmentation fault (core dumped)

To Reproduce

(Write what you did to reproduce the crash. Full source code is
appreciated. We also very much appreciate it if you try to narrow the
source down to a small stand-alone example.)

from __future__ import annotations
from typing import Callable

class Wrapper:
    def __call__[**P, T](
        self,
        func: Callable[P, T] | None = None,
    ) -> Callable[P, T] | Wrapper:
        if func is not None:
            return func

        return Wrapper()

Your Environment

• Mypy version used: 1.13.0
• Mypy command-line flags: N/A
• Mypy configuration options from mypy.ini (and other config files): N/A
• Python version used: 3.13.0
• Operating system and version: wsl 2.3.26.0

First reproduce the crash with the provided Wrapper example using mypy . --show-traceback under the reported environment. Trace the recursive generic-function handling in mypy and add a regression test for the example; done means mypy reports the source without a segmentation fault.