Pattern matching a dataclass with different field type fails for Python >= 3.13

Bug Report

Pattern matching on a dataclass with a field of different type than required by the dataclass fails with Cannot determine type of ... for Python 3.13 and higher

To Reproduce

3.12 working gist: https://mypy-play.net/?mypy=latest&python=3.12&gist=f2947a04a9a86defefd16e54c0133c84
3.13 failing gist: https://mypy-play.net/?mypy=latest&python=3.13&gist=f2947a04a9a86defefd16e54c0133c84

from dataclasses import dataclass

@dataclass
class A:
    pass

@dataclass
class B:
    pass

@dataclass
class C:
    sth: A

def func(c: C, b: B):
    match c:
        case C(B() as obj) if obj == b:
            print("matched")

Expected Behavior

I believe it should resolve the type same as for <= 3.12.

Actual Behavior

For Python >= 3.13 inferring obj type fails with:

repro.py:17: error: Cannot determine type of "obj"  [has-type]

Your Environment

• Mypy version used: 1.19.1
• Mypy command-line flags: mypy repro.py
• Mypy configuration options from mypy.ini (and other config files): no additional config
• Python version used: 3.13.5

Commencez par l’exemple repro.py et exécutez mypy 1.19.1 avec Python 3.12 et 3.13 en utilisant les cas du playground liés. Suivez le pattern matching et l’inférence de dataclass impliqués dans case C(B() as obj) ; le travail est terminé lorsque Python 3.13 infère obj de manière cohérente avec 3.12 sans l’erreur Cannot determine type.