Actually, I think the part that is cracked is the tubular receiver. The barrel screws into the receiver (really tight!), but technically it is a separate part. Unfortunately, in the Ruger .22 pistol design, that tube is the serial numbered part; "the gun" as the Feds might put it. That means you'll have to have ask Ruger to replace it, and depending on how they handle such things, you may end up with a different serial number once it is repaired. In my experience, Ruger is pretty good about warranty stuff.
I always thought that the receiver tube on Ruger pistols was fairly soft, having seen a few that were battered or peened over the years. To get the loaded chamber indicator to work correctly, maybe they had to harden that area on the tube, and that made it more susceptible to cracking.
As I said above, interesting...