Goal:
  
  x : V.t
  p : VSet.t
  H : VSet.In x p -> False
  a : V.t
  H0 : x = a
  H1 : VSet.In a p
  H2 : x = a
  ============================
   False


DEBUG:Going to execute:
match goal with
           | |- _ -> _ => intro; t_tauto_intuit
           | |- _ => t_reduce; t_solver
           end