Can classes in a module be used for arguments in the same module?

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Godot Version

4.3

Question

I am making a module, and I have a class where one of the exposed methods takes another class in that same module as an argument. When I compile Godot, I get an error that the type is not recognized and can’t be used.

If I swap the type for the exposed method to something like String, or some other Godot type, it works fine, so I know it is just this custom class type that is causing the issue. Is this possible? Or would I need to make some engine changes to allow for exposing custom types for a module’s API? Below will be an example of the classes and register_types.cpp

// MyClass.h
#ifndef MY_CLASS_H
#define MY_CLASS_H

#include "core/object/object.h"
#include "core/object/ref_counted.h"

class MyClass : public Object {
	GDCLASS(MyClass, Object);

protected:
        String data;
	static void _bind_methods() {
		ClassDB::bind_method(D_METHOD("set_data", "data"), &MyClass::set_data);
		ClassDB::bind_method(D_METHOD("get_data"), &MyClass::get_data);

		ADD_PROPERTY(PropertyInfo(Variant::STRING, "data", PROPERTY_HINT_NONE, "", PROPERTY_USAGE_NONE), "set_data", "get_data");
	}

	void set_data(const String &data) {
		this->data = data;
	}

	String get_data() const {
		return data;
	}

public:
	MyClass() {};
};

#endif // SUMMATOR_H


// ExposedClass.cpp
#include "ExposedClass.h"

ExposedClass::ExposedClass() {}

// The exposed types have to be godot types.
void ExposedClass::custom_method(MyClass msg) {
	// Do stuff
}

void ExposedClass::_bind_methods() {
	ClassDB::bind_method(D_METHOD("custom_method", "msg"), &ExposedClass::custom_method);
}


// register_types.cpp
#include "register_types.h"

#include "core/object/class_db.h"
#include "MyClass.h"
#include "ExposedClass.h"

void initialize_my_module_module(ModuleInitializationLevel p_level) {
	if (p_level != MODULE_INITIALIZATION_LEVEL_SCENE) {
		return;
	}
	ClassDB::register_class<MyClass>();
	ClassDB::register_class<ExposedClass>();
}

void uninitialize_my_module_module(ModuleInitializationLevel p_level) {
	if (p_level != MODULE_INITIALIZATION_LEVEL_SCENE) {
		return;
	}
   // Nothing to do here in this example.
}

With a setup similar to the one above, it will fail compilation with:

./core/variant/binder_common.h:690:40: error: incomplete type 'GetTypeInfo<MyClass, void>' used in nested name specifier
  690 |                 type = GetTypeInfo<Q>::VARIANT_TYPE;

I have tried going through and adding my type within the whole variant system, and I can kind of get it working, but it is a lot of changes in the engine to get it working. I would rather have it all contained in this or another module if possible, or if this is possible with gdextensions, I would be fine with something like that as well.

Thanks for any help!