Goal:
    x : V.t  s : VSet.t
  ============================
   (~ VSet.In x (VSet.remove x s))


DEBUG:Going to execute:
tryif prop (VSetDecide.MSetDecideAuxiliary.MSet_Prop P) holds by
            auto  100 with MSet_Prop then fail else clear H 
Level 1: Backtrace:

s is used in conclusion.
Level 1: Backtrace:

s is used in conclusion.
Level 1: Backtrace:

s is used in conclusion.