Goal:
    x : V.t  p : VSet.t  a : V.t  H1 : VSet.In a p  H0 : False
  ============================
   False


DEBUG:Going to execute:
match reverse goal with
           | |- ?X1 => <Coq.Init.Tauto.is_unit_or_eq> flags X1; constructor 1
           | H:?X1 |- _ => <Coq.Init.Tauto.is_empty> flags X1; elim H
           | _ => Ltac.assumption
           end