The PureMVC Framework Code at the Speed of Thought

First of all, excuse my poor english

I have been learning Flex for a month. Last week I downloaded and added to my project path library in FB3 the Pure MVC multicore 1.0.5 and Pipes 1.1 swc.

Also, I downloaded the Fabrication Utility swc, version 0.5.2

I fall in love with the FabricationRouting demo, and I downloaded it..
The problem is that I get a casting problem when I try to compile the shell :

line :       override protected function getStartupCommand() : Class {

I'm too newbie to solve theese.
Any ideas ?

Thanks in advance ...