Fix type inference of positional parameter in class pattern involving builtin subtype

[brianschubert]

Fixes #18140

Demo

from typing import reveal_type

class A(str):
    pass

class B(str):
    __match_args__ = ("b",)
    
    @property
    def b(self) -> int: return 1


match A("a"):
    case A(a):
        reveal_type(a)  # before: Revealed type is "__main__.A"
                        # after:  Revealed type is "__main__.A"
        print(type(a))  # output: <class '__main__.A'>

match B("b"):
    case B(b):
        reveal_type(b)  # before: Revealed type is "__main__.B"
                        # after:  Revealed type is "builtins.int"
        print(type(b))  # output: <class 'int'>

[github-actions]

According to mypy_primer, this change doesn't affect type check results on a corpus of open source code. ✅

[JukkaL]

Thanks for the fix!