Overloads in generic classes are extremely slow when using generic self

Bug Report

Performance of mypy degrades drastically with the number of type variable constraints when checking overloaded method of generic class with overloaded self.

To Reproduce

from typing import TypeVar, Generic, TypeAlias, overload, Any


T1 = TypeVar('T1', int, str, bool)
T2 = TypeVar('T2', int, str, bool)
T3 = TypeVar('T3', int, str, bool)
T4 = TypeVar('T4', int, str, bool)
T5 = TypeVar('T5', int, str, bool)
T6 = TypeVar('T6', int, str, bool)
T7 = TypeVar('T7', int, str, bool)


class A(Generic[T1, T2, T3, T4, T5, T6, T7]):
    @overload
    def foo(self: A[int, T2, T3, T4, T5, T6, T7]) -> int:
        ...
    
    @overload
    def foo(self: A[str, T2, T3, T4, T5, T6, T7]) -> str:
        ...
        
    def foo(self) -> int | str:
        raise NotImplementedError

https://mypy-play.net/?mypy=latest&python=3.12&gist=fd939322936206cbb9b1f45a71fbd9b7

Expected Behavior

Code typechecks in realistic time. For reference pyrights checks such code without significant performance issues

Actual Behavior

mypy-play.net times out. In my experience it takes at least more than 10 minutes to check such code. Interestingly, when converting foo method to an independent function taking A as a parameter typechecking time drops significantly.

Your Environment

python3.11 and python3.12, both mypy 1.12.1 and 1.13

Start with the supplied Python reproduction and mypy-play link, then compare its checking time with the independent-function variant described in the report. Measure how runtime changes as the number of constrained type variables grows, and use the expected behavior—typechecking in realistic time—as the completion criterion.