glib: Remove SendWeakRef::new() because implementation is unsound

[quo]

Fixes #1617

Not sure whether it would be better to remove the Default impl too, I've kept it for now.

[sdroege]

Not sure whether it would be better to remove the Default impl too, I've kept it for now.

That seems OK and simplifies initializing struct fields.

[sdroege]

Do you also want to add a impl<T: ObjectType> From<T> for SendWeakRef<T> or some other kind of convenience constructor? Seems useful to me at least

[quo]

SendWeakRef::from(o.downgrade()) is good enough for me. Like you said, usually async channels are cleaner, so SendWeakRef probably shouldn't see all that much use.

If you do want to add a nicer API, I would make it similar to the WeakRef API. So something like obj.downgrade_send(), or obj.downgrade().send(), or maybe obj.ref_send() or obj.as_send()?

[sdroege]

Ok, let's keep it like this then :)