fix cast insertion for monotonic
fix cast insertion for monotonic

akuhlens/schml,akuhlens/schml,Gradual-Typing/Grift,akuhlens/schml,akuhlens/schml,Gradual-Typing/Grift,akuhlens/schml,Gradual-Typing/Grift,akuhlens/schml,Gradual-Typing/Grift