Goal:
  
  x : V.t
  s : VSet.t
  y : V.t
  H0 : x = y -> False
  H : VSet.In y s
  H2 : x = y -> False
  ============================
   (x = y)


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