ListenerToken assign operator copying an unique pointer

In the Base.hh header there is this operator:

       ListenerToken& operator=(ListenerToken &&other) {
            _token = other._token;
            _callback = other._callback;
            other._token = nullptr;
            return *this;

It cannot be used because the _callback member is of type std::unique_ptr.

Regarding Query::ChangeListener, it seems strange that the Query::ChangeListener owns the query and not the other way around, more so that Query::ChangeListener doesn’t have a working assign operator.

These wrappers work fine in simple sopes, but I find a bit complicated and unintuitive to manage a ChangeListener object, I don’t know if other users have this problem too.

@Ionut_Cosmin_Mihai : It would be quite helpful if you could give us just some basic information about your use caae. This is Couchbase Lite C? A recent version? You are building with, maybe, clang?

Yes, this is Couchbase Lite C, last master commit wich today is 6e033f5d9b21c92ad6e04819987b6325d6cb59ac . The implementation is the same on release/lithium.
The compiler I usd is MSVC(we are also using clang) but copying a std::unique_ptr doesn’t work on any compiler.
Here is the case (This will not compile, so I am referring to building only, not to functionality.):

class QueryManager
	ReplicatorManager() = default;
	~ReplicatorManager() = default;

	void createQuery(cbl::Database& database)
		q = cbl::Query(database, kCBLN1QLLanguage, "REQUEST EXAMPLE");

		// This will result in: 
		// Error	C2280	'std::unique_ptr<std::function<void (cbl::Query::Change)>,std::default_delete<std::function<void (cbl::Query::Change)>>> &std::unique_ptr<std::function<void (cbl::Query::Change)>,std::default_delete<std::function<void (cbl::Query::Change)>>>::operator =(const std::unique_ptr<std::function<void (cbl::Query::Change)>,std::default_delete<std::function<void (cbl::Query::Change)>>> &)': attempting to reference a deleted function	ConsoleApplicationCouchbase	include\cbl++\Base.hh
		// This error can be workedaround by having instead a std::shared_ptr<cbl::Query::ChangeListener>
		changeListener = q.addChangeListener([](cbl::Query::Change change) {
			std::cout << "Print something on change";
		// Next, if we look into the addChangeListener implementation we see that the ownership of q is given to the Query::ChangeListener object. Before the addChangeListener call is finished, q is not owned by this class, but by the changeListener member.


	cbl::Query q;
	cbl::Query::ChangeListener changeListener;

I think it is a common case to manage a query object like this(maybe having a map of queries), I am wondering if it is supposed to be used in another way. Also it is not clear for me how the objects should be destroyed in this case.
Thanks for help!

This seems to be a bug to me. I have created