Goal:
    x1 : V.t  n1 : Z  y1 : V.t  x2 : V.t  n2 : Z  y2 : V.t  H : V.lt x2 x1
  ============================
   (V.lt x2 x1 \/
    V.eq x2 x1 /\ n2 < n1 \/ V.eq x2 x1 /\ n2 = n1 /\ V.lt y2 y1)


DEBUG:Going to execute:
solve [ Ltac.left; t_tauto_intuit | Ltac.right; t_tauto_intuit ]
Level 2: evaluation returns
<coq-core.plugins.tauto::is_disj@0>
where
tauto_flags := 
of type
tauto_flags
X1 := V.lt x2 x1 \/
      V.eq x2 x1 /\ n2 < n1 \/ V.eq x2 x1 /\ n2 = n1 /\ V.lt y2 y1
of type
constr of type tacvalue