fix parser conflict between case labels and pair expressions.
fix parser conflict between case labels and pair expressions.

iamrekcah/clay,jckarter/clay,iamrekcah/clay,iamrekcah/clay,aep/clay,mario-campos/clay,aep/clay,mario-campos/clay,jckarter/clay,aep/clay,jckarter/clay,mario-campos/clay,aep/clay,mario-campos/clay,aep/clay,aep/clay,iamrekcah/clay,iamrekcah/clay,jckarter/clay,jckarter/clay,jckarter/clay,mario-campos/clay