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Combining @dataclass and NamedTuple leads to crash in Python 3.13+ #18982

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smheidrich opened this issue Apr 27, 2025 · 1 comment
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Combining @dataclass and NamedTuple leads to crash in Python 3.13+ #18982

smheidrich opened this issue Apr 27, 2025 · 1 comment
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@smheidrich
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Crash Report

When being told to typecheck a module that contains a class which is both derived from NamedTuple and decorated with @dataclass (probably by mistake, but no matter), Mypy installed in a Python 3.13+ environment will crash.

It seems to work fine for Python < 3.13.

Traceback

Traceback (most recent call last):
  File ".../bin/mypy", line 12, in <module>
    sys.exit(console_entry())
             ~~~~~~~~~~~~~^^
  File ".../mypy/__main__.py", line 15, in console_entry
    main()
    ~~~~^^
  File "mypy/main.py", line 119, in main
  File "mypy/main.py", line 203, in run_build
  File "mypy/build.py", line 191, in build
  File "mypy/build.py", line 267, in _build
  File "mypy/build.py", line 2937, in dispatch
  File "mypy/build.py", line 3335, in process_graph
  File "mypy/build.py", line 3430, in process_stale_scc
  File "mypy/semanal_main.py", line 99, in semantic_analysis_for_scc
  File "mypy/semanal_main.py", line 443, in apply_class_plugin_hooks
  File "mypy/semanal_main.py", line 479, in apply_hooks_to_class
  File "mypy/plugins/dataclasses.py", line 969, in dataclass_class_maker_callback
  File "mypy/plugins/dataclasses.py", line 392, in transform
  File "mypy/plugins/dataclasses.py", line 412, in _add_dunder_replace
  File "mypy/plugins/common.py", line 238, in add_method_to_class
  File "mypy/plugins/common.py", line 314, in _prepare_class_namespace
ValueError: list.remove(x): x not in list

To Reproduce

Create a file named bug.py with these contents:

from typing import NamedTuple
from dataclasses import dataclass

@dataclass
class A(NamedTuple):
  a: int
  b: str

Run Mypy installed in a Python 3.13 environment on this file, e.g. using uvx:

uvx --python 3.13 --reinstall mypy --show-traceback bug.py

Replacing 3.13 with 3.12 or earlier, you can check that it worked fine for earlier Python versions.

Your Environment

  • Mypy version used: 1.15.0 (compiled: yes)
  • Mypy command-line flags: None needed
  • Mypy configuration options from mypy.ini (and other config files): None needed
  • Python version used: 3.13+ required to reproduce this
  • Operating system and version: Debian Linux 12 (bookworm), but also happened on another machine running some version of Ubuntu
@smheidrich smheidrich changed the title Combining @dataclass and NamedTuple leads to Mypy crash in Python 3.13+ Combining @dataclass and NamedTuple leads to crash in Python 3.13+ Apr 27, 2025
@smheidrich
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Never mind, this was already reported in #18527 and has gotten fixed between 1.15.0 and the current master, so I guess it's just a matter of waiting for the next release.

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