Cannot use FromPyObject + IntoPyObject with #[pyo3(default)]

[bbstilson]

Bug Description

This #4643 PR introduced the #[pyo3(default)] attribute macro. Unfortunately, it doesn't work when both FromPyObject and IntoPyObject are derived for the same object.

Steps to Reproduce

Compiles fine:

#[derive(FromPyObject)]
struct Foo {
    #[pyo3(default)]
    x: Option<String>
}

This does not:

#[derive(FromPyObject, IntoPyObject)]
struct Foo {
    #[pyo3(default)]
    x: Option<String>
}

error: expected one of: `attribute`, `item`, `into_py_with`
   --> src/foo.rs:3:12
    |
122 |     #[pyo3(default)]
    |            ^^^^^^^

Backtrace

Your operating system and version

Ubuntu 22

Your Python version (python --version)

Python 3.10.12

Your Rust version (rustc --version)

rustc 1.85.0 (4d91de4e4 2025-02-17)

Your PyO3 version

0.24.0

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

venv

Additional Info

No response

[Icxolu]

See also #4884

[bbstilson]

@Icxolu sorry I missed that one! I did a search for default and didn't find anything. Feel free to close this if this is just a subset of the problem captured in #4884