[New-bugs-announce] [issue33100] dataclasses and __slots__ - non-default argument (member_descriptor)

[Adrian Stachlewski]

New submission from Adrian Stachlewski <adrian.stachlewski at gmail.com>:

I've tried to declare two classes

@dataclass
class Base:
    __slots__ = ('x',)
    x: Any


@dataclass
class Derived(Base):
    x: int
    y: int

As long as I correctly understood PEP 557 (inheritance part), changing type of variable is possible. This code produce error:

TypeError: non-default argument 'y' follows default argument

'x' variable in Derived class has changed default from MISSING to member_descriptor and that's the reason of the exception.

----------
components: Library (Lib)
messages: 314077
nosy: stachel
priority: normal
severity: normal
status: open
title: dataclasses and __slots__ - non-default argument (member_descriptor)
type: behavior
versions: Python 3.7, Python 3.8

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Python tracker <report at bugs.python.org>
<https://bugs.python.org/issue33100>
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