Yes, we know we aren't going to implement generalized existentials before ABI stability, and we know we'll need to migrate some standard library type erasers to proper existentials at some point in the future when we do properly support them.Yes, we know we aren't going to implement generalized existentials before ABI stability, and we know we'll need to migrate some standard library type erasers to proper existentials at some point in the future when we do properly support them.