Goal:
  
  y1 : V.t
  n2 : Z
  y2 : V.t
  x3 : V.t
  n3 : Z
  y3 : V.t
  H1'' : V.lt y1 y2
  H2' : n2 < n3
  T1 : V.lt x3 x3 -> V.lt x3 x3 -> V.lt x3 x3
  H : V.lt y2 y3 -> V.lt y1 y3
  H0 : n2 = n3 -> n2 = n3
  ============================
   (x3 = x3)


DEBUG:Going to execute:
<Coq.Init.Tauto.flatten_contravariant_conj> flags X1 X2 id
Level 4: evaluation returns
<coq-core.plugins.tauto::flatten_contravariant_conj@0>
where
tauto_flags := 
of type
tauto_flags
id := H
of type
constr
X2 := V.lt y1 y3
of type
constr
X1 := V.lt y2 y3
of type
constr of type tacvalue

Level 4: Backtrace:

Tactic failure.
Level 4: Backtrace:

Tactic failure.
Level 3: Backtrace:

Tactic failure.