cannot bind rvalue reference of type .. to lvalue of type .. / pointer argument requires that the function be marked unsafe

[lnicola]

Describe the bug
I'm getting the error in the issue.

To Reproduce

use autocxx::prelude::*;
use autocxx::subclass::*;

include_cpp! {
    #include "gdal/gdal_priv.h"
    safety!(unsafe_ffi)
    generate!("GDALDataset")
    subclass!("GDALDataset", MyDataset)
}

use ffi::*;

#[subclass]
#[derive(Default)]
pub struct MyDataset;

impl GDALDataset_methods for MyDataset {}

fn main() {}

Expected behavior
I'd like it to work.

Additional context
Requires gdal-devel or similar.

EDIT: dropping safety!(unsafe_ffi) fixes this, but then it fails with error: cannot bind rvalue reference of type ‘std::unique_ptr<GDALRelationship>&&’ to lvalue of type ‘std::unique_ptr<GDALRelationship>’.

[adetaylor]

Please raise a bug PR per https://google.github.io/autocxx/reporting_bugs.html