casting and unwrapping at the same time

[bjartek]

In the curent metadata standard there is a method
fun resolveView(_ type:Type) : AnyStruct?

When you call that method you very often want to cast the resulting object as the type you sent in. So something like this?

let metadata=collection.borrowViewResolver(id: id).resolveView(Type<Voucher.Metadata>()) as! Voucher.Metadata

This gives no compile error as you have use as! but it will never succeed. The reason is that since resolveView returns an option you first have to unrwap it and then cast it. So this code will work

let metadata=collection.borrowViewResolver(id: id).resolveView(Type<Voucher.Metadata>())! as! Voucher.Metadata

Another issue I am pondering is why we need as! here. If i remove it i get
mismatched types. expected Vouchre.Metadata?, got AnyStruct? but I have clearly ! the value before i cast it.

[turbolent]

I think with #3580 this should be supported now.