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

repro.py の例から始め、リンクされた playground のケースを使って Python 3.12 および 3.13 上で mypy 1.19.1 を実行します。case C(B() as obj) に関係するパターンマッチングと dataclass の推論を追跡します。Python 3.13 が Cannot determine type エラーなしで 3.12 と一貫して obj を推論できれば完了です。