Internal error on mypy of `dataclass` with `TypedDict` as `ClassVar`

Bắt đầu với mypy/plugins/dataclasses.py, đặc biệt là collect_attributes(), và tái hiện sự cố bằng script tối thiểu với --strict và --show-traceback. Theo dõi cách ClassVar chứa một TypedDict được xử lý; hoàn thành nghĩa là mypy không còn gây ra INTERNAL ERROR cho ví dụ này mà thay vào đó hoàn tất việc kiểm tra kiểu một cách bình thường.

Crash Report

When type-checking (--strict or not) a simple script with dataclass, ClassVar and TypedDict (all three components required, omitting any of three resolves the issue), mypy reports "error: INTERNAL ERROR".

Traceback

(.venv) C:\...\mypybug\mypy>mypy --strict --show-traceback test.py
test.py: error: INTERNAL ERROR -- Please try using mypy master on GitHub:
https://mypy.readthedocs.io/en/stable/common_issues.html#using-a-development-mypy-build
Please report a bug at https://github.com/python/mypy/issues
version: 2.4.0+dev.6934a9d01cab6226a64b38642e124368f8ddc653
Traceback (most recent call last):
  File "<frozen runpy>", line 203, in _run_module_as_main
  File "<frozen runpy>", line 88, in _run_code
  File "C:\...\mypybug\mypy\.venv\Scripts\mypy.exe\__main__.py", line 5, in <module>
    sys.exit(console_entry())
  File "C:\...\mypybug\mypy\.venv\Lib\site-packages\mypy\__main__.py", line 16, in console_entry
    main()
  File "C:\...\mypybug\mypy\.venv\Lib\site-packages\mypy\main.py", line 154, in main
    res, messages, blockers = run_build(sources, options, fscache, t0, stdout, stderr)
  File "C:\...\mypybug\mypy\.venv\Lib\site-packages\mypy\main.py", line 244, in run_build
    res = build.build(sources, options, None, flush_errors, fscache, stdout, stderr)
  File "C:\...\mypybug\mypy\.venv\Lib\site-packages\mypy\build.py", line 422, in build
    result = build_inner(
  File "C:\...\mypybug\mypy\.venv\Lib\site-packages\mypy\build.py", line 537, in build_inner
    graph = dispatch(sources, manager, stdout, connect_threads)
  File "C:\...\mypybug\mypy\.venv\Lib\site-packages\mypy\build.py", line 4150, in dispatch
    process_graph(graph, manager)
  File "C:\...\mypybug\mypy\.venv\Lib\site-packages\mypy\build.py", line 4618, in process_graph
    done, still_working, results = manager.wait_for_done(graph)
  File "C:\...\mypybug\mypy\.venv\Lib\site-packages\mypy\build.py", line 1484, in wait_for_done
    process_stale_scc(graph, next_scc, self)
  File "C:\...\mypybug\mypy\.venv\Lib\site-packages\mypy\build.py", line 4786, in process_stale_scc
    mypy.semanal_main.semantic_analysis_for_scc(graph, scc, manager.errors)
  File "C:\...\mypybug\mypy\.venv\Lib\site-packages\mypy\semanal_main.py", line 97, in semantic_analysis_for_scc
    apply_class_plugin_hooks(graph, scc, errors)
  File "C:\...\mypybug\mypy\.venv\Lib\site-packages\mypy\semanal_main.py", line 466, in apply_class_plugin_hooks
    with state.wrap_context():
  File "C:\Program Files\Python313\Lib\contextlib.py", line 162, in __exit__
    self.gen.throw(value)
  File "C:\...\mypybug\mypy\.venv\Lib\site-packages\mypy\build.py", line 3075, in wrap_context
    yield
  File "C:\...\mypybug\mypy\.venv\Lib\site-packages\mypy\semanal_main.py", line 469, in apply_class_plugin_hooks
    if not apply_hooks_to_class(
           ~~~~~~~~~~~~~~~~~~~~^
        state.manager.semantic_analyzer,
        ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    ...<4 lines>...
        errors,
        ^^^^^^^
    ):
    ^
  File "C:\...\mypybug\mypy\.venv\Lib\site-packages\mypy\semanal_main.py", line 505, in apply_hooks_to_class
    ok = ok and hook(ClassDefContext(defn, decorator, self))
                ~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "C:\...\mypybug\mypy\.venv\Lib\site-packages\mypy\plugins\dataclasses.py", line 974, in dataclass_class_maker_callback
    return transformer.transform()
           ~~~~~~~~~~~~~~~~~~~~~^^
  File "C:\...\mypybug\mypy\.venv\Lib\site-packages\mypy\plugins\dataclasses.py", line 238, in transform
    attributes = self.collect_attributes()
  File "C:\...\mypybug\mypy\.venv\Lib\site-packages\mypy\plugins\dataclasses.py", line 603, in collect_attributes
    assert isinstance(node, Var), node
           ~~~~~~~~~~^^^^^^^^^^^
AssertionError: TypeInfo(
  Name(test.X.TD)
  Bases(typing._TypedDict)
  Mro(test.X.TD, typing._TypedDict, typing.Mapping, typing.Collection, typing.Iterable, typing.Container, builtins.object)
  Names())

test.py: note: use --pdb to drop into pdb

To Reproduce

This code triggers the issue:

import dataclasses
from typing import ClassVar, TypedDict


@dataclasses.dataclass
class X:
    a: int
    TD: ClassVar = TypedDict('TD', {'a': int})

Your Environment

• Mypy version used: mypy 2.4.0+dev.6934a9d01cab6226a64b38642e124368f8ddc653 (compiled: no)
• Mypy command-line flags: --strict
• Mypy configuration options from mypy.ini (and other config files): none
• Python version used: 3.13.15
• Operating system and version: Windows