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Multiple inheritance error when using slots #667
Description
The following classes definitions causes an error:
@attr.s(auto_attribs=True, frozen=True, slots=True, collect_by_mro=True)
class Foo:
foo: str
@attr.s(auto_attribs=True, frozen=True, slots=True, collect_by_mro=True)
class Bar:
bar: str
@attr.s(auto_attribs=True, frozen=True, slots=True, collect_by_mro=True)
class Baz(Foo, Bar):
baz: str> class Baz(Foo, Bar):
E TypeError: multiple bases have instance lay-out conflict
Note that this error occurs on master with a commit that seems to purport to fix this problem:
#635
Removing the slots decorator kwargs resolves the error.
Is there a workaround that supports slots?
Activity
[-]Multiple inheritance error[/-][+]Multiple inheritance error when using slots[/+]hynek commentedon Aug 18, 2020
To be clear: #635 has nothing to do with this problem and the problem exists in 19.3 too.
I suspect it's related to the way we create slotted classes in
attrs/src/attr/_make.py
Line 711 in b02335f
Since slots become True by default in NG, we should have a look if we can fix this.
Tinche commentedon Aug 18, 2020
An even smaller test case:
Tinche commentedon Aug 18, 2020
Actually, C doesn't even have to be an attrs class:
In fact, browsing the Python docs (https://docs.python.org/3/reference/datamodel.html#notes-on-using-slots):
So this is a Python limitation.
hynek commentedon Aug 19, 2020
Thank you for the research Tin! I will add an entry to the glossary.
jacobg commentedon Aug 19, 2020
@Tinche @hynek Thank you for looking into this issue!