P : @<X: y> { X print("Doesn't work!") }
P : @<X: Y> { X print("Doesn't work as well!") }
#---
#x
#---
#ERR:Line 1, column 7: Generic 'X' defines consumable, but 'y' is not consuming
#ERR:Line 1, column 10: Use of undefined name 'y'
#ERR:Line 2, column 10: Use of undefined name 'Y'