attribute set_all does not work on complex enums

[DanielT]

Bug Description

I can annotate a complex enum as #[pyclass(get_all, set_all)], but set_all does not work.
It should either work or be rejected during compilation.

Steps to Reproduce

To demonstrate the issue I wrote the following code:

use pyo3::prelude::*;

#[pyclass(get_all, set_all)]
#[derive(Debug, Clone)]
struct ItemValues {
    number: u8,
}

#[pymethods]
impl ItemValues {
    #[new]
    fn new(number: u8) -> Self {
        ItemValues { number }
    }

    fn __repr__(&self) -> String {
        format!("{:#?}", self)
    }
}

#[pyclass(get_all, set_all)]
#[derive(Debug, Clone)]
enum ComplexEnum {
    Item(ItemValues),
    OtherItem {
        value: usize,
    },
}

#[pymethods]
impl ComplexEnum {
    fn __repr__(&self) -> String {
        format!("{:#?}", self)
    }
}

#[pymodule]
fn pyo3_test(m: &Bound<'_, PyModule>) -> PyResult<()> {
    m.add_class::<ItemValues>()?;
    m.add_class::<ComplexEnum>()?;
    Ok(())
}

After building and installing the module, I tested it in the REPL:

>>> from pyo3_test import *
>>> enumval = ComplexEnum.Item(ItemValue(55))
>>> enumval
Item(
    ItemValues {
        number: 55,
    },
)
>>> enumval[0].number = 1
>>> enumval
Item(
    ItemValues {
        number: 55,
    },
)

In this first test we see that writing to the number did not raise an error, but had no effect.

Next I try to set the value of OtherItem:

>>> other = ComplexEnum.OtherItem(3)
>>> other
OtherItem {
    value: 3,
}
>>> other.value = 4
Traceback (most recent call last):
  File "<python-input-9>", line 1, in <module>
    other.value = 4
    ^^^^^^^^^^^
AttributeError: attribute 'value' of 'builtins.ComplexEnum_OtherItem' objects is not writable

This at least raises an error, which is better than discarding thewrite silently, but it is still unexpected considering the set_all attribute was accepted.

Backtrace

Your operating system and version

Windows 10

Your Python version (python --version)

Python 3.13.2

Your Rust version (rustc --version)

rustc 1.85.0

Your PyO3 version

0.23.4

How did you install python? Did you use a virtualenv?

Yes, I'm using a virtualenv

Additional Info

No response