[smart_holder] Using a factory function custom constructor that returns a smart_holder

[Dann239]

I have a binding for a class Foo that uses a factory function init:

#include <pybind11/pybind11.h>

namespace py = pybind11;

struct Foo {};

PYBIND11_MODULE(test, test) {
    py::class_<Foo, std::shared_ptr<Foo>>(test, "Foo")
        .def(py::init([] {
            auto foo = std::shared_ptr<Foo>(new Foo());
            // do something with foo
            return foo;
        }));
}

I would like to convert it to use the smart_holder. So far i did this (i'm using the conservative approach):

#include <pybind11/pybind11.h>
#include <pybind11/smart_holder.h>

namespace py = pybind11;

struct Foo {};
PYBIND11_SMART_HOLDER_TYPE_CASTERS(Foo)

PYBIND11_MODULE(test, test) {
    py::classh<Foo>(test, "Foo")
        .def(py::init([] {
            auto foo = py::smart_holder::from_raw_ptr_take_ownership(new Foo());
            // do something with foo
            return foo;
        }));
}

However, it does not compile (i'm using gcc-11.2):

pybind11/detail/init.h:106:19: error: static assertion failed: pybind11::init(): init function must return a compatible pointer, holder, or value
  106 |     static_assert(!std::is_same<Class, Class>::value /* always false */,
      |                   ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

What am i doing wrong? What is the proper way to do this?

Thanks!