finalize IR case classes (#2611)
finalize IR case classes (#2611)

Without the final modified, these case classes may be
subclassed by third aprty arbitrary classes.
danking/hail,danking/hail,cseed/hail,hail-is/hail,cseed/hail,cseed/hail,danking/hail,danking/hail,hail-is/hail,cseed/hail,hail-is/hail,cseed/hail,hail-is/hail,cseed/hail,danking/hail,hail-is/hail,danking/hail,hail-is/hail,cseed/hail,hail-is/hail,danking/hail,hail-is/hail,cseed/hail,danking/hail