Goal:
  
  n1 : Z
  y1 : V.t
  n2 : Z
  y2 : V.t
  x3 : V.t
  n3 : Z
  y3 : V.t
  H1' : n1 < n2
  H2' : n2 < n3
  T1 : V.lt x3 x3 -> V.lt x3 x3 -> V.lt x3 x3
  T2 : V.lt y1 y2 -> V.lt y2 y3 -> V.lt y1 y3
  T3 : n1 = n2 -> n2 = n3 -> n1 = n3
  ============================
   (n1 < n3)


DEBUG:Going to execute:
<coq-core.plugins.tauto::is_conj@0>

Goals:
  
  n1 : Z
  y1 : V.t
  n2 : Z
  y2 : V.t
  x3 : V.t
  n3 : Z
  y3 : V.t
  H1' : n1 < n2
  H2' : n2 < n3
  T1 : V.lt x3 x3 -> V.lt x3 x3 -> V.lt x3 x3
  T2 : V.lt y1 y2 -> V.lt y2 y3 -> V.lt y1 y3
  T3 : n1 = n2 -> n2 = n3 -> n1 = n3
  ============================
   (x3 = x3)

  
  n1 : Z
  y1 : V.t
  n2 : Z
  y2 : V.t
  x3 : V.t
  n3 : Z
  y3 : V.t
  H1' : n1 < n2
  H2' : n2 < n3
  T1 : V.lt x3 x3 -> V.lt x3 x3 -> V.lt x3 x3
  T2 : V.lt y1 y2 -> V.lt y2 y3 -> V.lt y1 y3
  T3 : n1 = n2 -> n2 = n3 -> n1 = n3
  ============================
   (n1 < n3)


DEBUG:Going to execute:
<Coq.Init.Tauto.axioms> flags ||
             match reverse goal with
             | id:(?X1 -> ?X2) -> ?X3
               |- _ =>
                   Ltac.cut X3;
                    [ intro; clear id; t_tauto_intuit
                    | Ltac.cut (X1 -> X2);
                       [ exact
                       id
                       | generalize (fun y : X2 => id (fun x : X1 => y));
                          intro; clear id; (solve 
                          [ t_tauto_intuit ]) ] ]
             | id:~ ?X1 -> ?X3
               |- _ =>
                   Ltac.cut X3;
                    [ intro; clear id; t_tauto_intuit
                    | Ltac.cut (~ X1);
                       [ exact
                       id
                       | clear id; intro; (solve [ t_tauto_intuit ]) ] ]
             | |- ?X1 =>
                   <Coq.Init.Tauto.is_disj> flags X1; (solve
                    [ Ltac.left; t_tauto_intuit
                    | Ltac.right; t_tauto_intuit ])
             end ||
               match goal with
               | |- _ -> _ => intro; t_tauto_intuit
               | |- _ => t_reduce; t_solver
               end || t_solver
Level 4: evaluation returns
<coq-core.plugins.tauto::is_conj@0>
where
tauto_flags := 
of type
tauto_flags
X1 := n1 < n3
of type
constr of type tacvalue

Level 4: Backtrace:

Tactic failure.
Level 4: Backtrace:

Tactic failure.
Level 3: Backtrace:

Tactic failure.
Level 3: Backtrace:

Tactic failure.
Level 2: Backtrace:

No matching clauses for match.
Level 2: Backtrace:

No matching clauses for match.