Goal:
  
  x1 : V.t
  n1 : Z
  y1 : V.t
  n2 : Z
  y2 : V.t
  x3 : V.t
  n3 : Z
  y3 : V.t
  H1 : V.lt x1 x3
  H2' : n2 < n3
  T2 : V.lt y1 y2 -> V.lt y2 y3 -> V.lt y1 y3
  T3 : n1 = n2 -> n2 = n3 -> n1 = n3
  H : V.lt x3 x3 -> V.lt x1 x3
  ============================
   ((n2 = n3 -> n1 = n3) ->
    V.lt x1 x3 \/ x1 = x3 /\ n1 < n3 \/ x1 = x3 /\ n1 = n3 /\ V.lt y1 y3)


DEBUG:Going to execute:
intro; clear id
Level 2: evaluation returns
<coq-core.plugins.ltac::cut@0>
where
$1 := n2 = n3 -> n1 = n3
of type
constr of type tacvalue