Goal:
    y1 : V.t  x2 : V.t  n2 : Z  y2 : V.t  H : V.lt y1 y2
  ============================
   (V.lt x2 x2 \/
    V.eq x2 x2 /\ n2 < n2 \/ V.eq x2 x2 /\ n2 = n2 /\ V.lt y1 y2)


DEBUG:Going to execute:
<Coq.Init.Tauto.is_disj> flags X1; elim id; intro; clear id
Level 2: evaluation returns
<coq-core.plugins.tauto::is_disj@0>
where
tauto_flags := 
of type
tauto_flags
X1 := Z
of type
constr of type tacvalue

Level 2: Backtrace:

Tactic failure.
Level 2: Backtrace:

Tactic failure.
Level 1: Backtrace:

Tactic failure.
Level 1: Backtrace:

Tactic failure.
Level 1: Backtrace:

Tactic failure.
Level 1: Backtrace:

Tactic failure.