[New-bugs-announce] [issue33453] from __future__ import annotations breaks dataclasses ClassVar handling

[Rick Teachey]

New submission from Rick Teachey <ricky at teachey.org>:

This is broken in 3.7 (both beta 3 and 4):

from __future__ import annotations
from dataclasses import dataclass
from typing import ClassVar, Any

@dataclass
class C():
    class_var: ClassVar[Any] = object()
    data: str

Traceback:

Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "C:\Users\ricky\AppData\Local\Programs\Python\Python37\lib\dataclasses.py", line 850, in dataclass
    return wrap(_cls)
  File "C:\Users\ricky\AppData\Local\Programs\Python\Python37\lib\dataclasses.py", line 842, in wrap
    return _process_class(cls, init, repr, eq, order, unsafe_hash, frozen)
  File "C:\Users\ricky\AppData\Local\Programs\Python\Python37\lib\dataclasses.py", line 763, in _process_class
    else 'self',
  File "C:\Users\ricky\AppData\Local\Programs\Python\Python37\lib\dataclasses.py", line 442, in _init_fn
    raise TypeError(f'non-default argument {f.name!r} '
TypeError: non-default argument 'data' follows default argument

----------
components: Library (Lib)
messages: 316333
nosy: Ricyteach, eric.smith
priority: normal
severity: normal
status: open
title: from __future__ import annotations breaks dataclasses ClassVar handling
type: behavior
versions: Python 3.7

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Python tracker <report at bugs.python.org>
<https://bugs.python.org/issue33453>
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