Goal:
  
  x : V.t
  y : V.t
  p : VSet.t
  H : x = y -> False
  a : V.t
  H0 : y = a
  H3 : y = a -> False
  H1 : VSet.In a p
  ============================
   (x = a \/ VSet.In a p /\ y <> a)


DEBUG:Going to execute:
F x2 x1 x0
Level 3: evaluation returns
<coq-core.plugins.tauto::find_cut@0>
where
k := fun id0 id1 X2 => assert X2; [ exact (id0 id1) | clear id0 ]
     where
     flags := 
     of type
     tauto_flags
of type
tacvalue of type tacvalue