Goal:
  
  G : t
  HI : invariants G
  HG : acyclic_no_loop G
  n : Z
  x : V.t
  y : V.t
  Vy : VSet.In y (V G) -> False
  Hle : leq_vertices G n x y
  e : y = y
  Hy : x = y
  XX : Z.of_nat (to_label (lsp G (s G) x)) + n <=
       Z.of_nat (to_label (lsp G (s G) x))
  ============================
   (n <= 0)


DEBUG:Going to execute:
<Coq.Init.Tauto.find_cut>
            ltac:(fun id0 id1 X2 =>
                    assert X2; [ exact (id0 id1) | clear id0 ])
Level 2: evaluation returns
<coq-core.plugins.tauto::is_disj@0>
where
tauto_flags := 
of type
tauto_flags
X1 := Z.of_nat (to_label (lsp G (s G) x)) + n <=
      Z.of_nat (to_label (lsp G (s G) x))
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.