[FEATURE REQUEST] downcast/upcast on Option<Object>

[ranfdev]

There are many cases where gtk returns an Option<Widget> which must be downcasted.
Doing let label: gtk::Label = list_item.child().unwrap().downcast().unwrap(); is not fun (note: child() returns Option<Widget>).

Implementing downcast and upcast for Option<Widget> would remove an unwrap.
I think it makes sense. In OOP languages you can have null objects, and null objects can be downcasted to null subclassess, can't they? (Edit: in Java you can upcast a null, but not downcast it. In any case, if we return a Result when downcasting, everything is alright)

[sdroege]

How about let label = list_item.child().and_then(|c| child.downcast::<gtk::Label>().ok()).unwrap()?

[ranfdev]

That's even longer than before

[ranfdev]

// current
let label: gtk::Label = list_item.child().unwrap().downcast().unwrap();
// your solution
let label = list_item.child().and_then(|c| c.downcast::<gtk::Label>().ok()).unwrap()
// with downcast on Option<Object>
let label: gtk::Label = list_item.child().downcast().unwrap();

[bilelmoussaoui]

This is a duplicate of #497

[sdroege]

I don't know, the and_then() solution seems most Rust-y to me. But give it a try if you can implement it on Option in a way that behaves well :)