Goal:
    G : t  HI : invariants G  HG : acyclic_no_loop G  n : Z  x : V.t  y : V.t
  ============================
   (V.eq_dec x y = true <-> x = y)


DEBUG:Going to execute:
destruct (V.eq_dec x y); cbn; intuition
DEBUG LTAC Evaluated term: orb_true_iff
DEBUG LTAC Evaluated term: Morphisms_Prop.or_iff_morphism