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{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"mypy generates `__match_args__` for dataclasses and `NamedTuple`s on Python \u003c3.10","articleBody":"**Bug Report**\r\n\r\nNot a big deal, but mypy appears to generate `__match_args__` for dataclasses and `NamedTuple`s even when running with `--python-version` set to 3.9:\r\n\r\n```python\r\nfrom dataclasses import dataclass\r\nfrom typing import NamedTuple\r\n\r\n@dataclass\r\nclass One:\r\n    bar: int\r\n\r\nf: One\r\nreveal_type(f.__match_args__)  # Revealed type is \"Tuple[Literal['bar']]\"\r\n\r\nclass Two(NamedTuple):\r\n    baz: str\r\n\r\ng: Two\r\nreveal_type(g.__match_args__)  # Revealed type is \"Tuple[Literal['baz']]\"\r\n```\r\n\r\n**Expected Behavior**\r\n\r\nMypy should not autogenerate `__match_args__` when running with `--python-version` set to \u003c3.10, as pattern-matching is new in 3.10.\r\n\r\n**Your Environment**\r\n\r\n- Mypy version used: `0.950+dev.a33d2353a81d075850a487f3913720037f2473aa (compiled: no)`\r\n- Mypy command-line flags: `--python-version 3.9`\r\n- Mypy configuration options from `mypy.ini` (and other config files): None\r\n- Python version used: 3.10\r\n- Operating system and version: Windows\r\n","author":{"url":"https://github.com/AlexWaygood","@type":"Person","name":"AlexWaygood"},"datePublished":"2022-03-29T21:29:14.000Z","interactionStatistic":{"@type":"InteractionCounter","interactionType":"https://schema.org/CommentAction","userInteractionCount":6},"url":"https://github.com/12489/mypy/issues/12489"}