Goal:
    G : t  HI : invariants G  HG : acyclic_no_loop G  b : bool
  ============================
   (~~ b <-> ~ b)


DEBUG:Going to execute:
f x
Level 2: evaluation returns
<coq-core.plugins.tauto::with_uniform_flags@0>
where
f := fun flags => <Coq.Init.Tauto.intuition_gen> flags tac
     where
     tac := try congruence
     of type
     tacvalue
of type
tacvalue of type tacvalue

Level 1: evaluation returns
<coq-core.plugins.tauto::with_uniform_flags@0>
where
f := fun flags => <Coq.Init.Tauto.intuition_gen> flags tac
     where
     tac := try congruence
     of type
     tacvalue
of type
tacvalue of type tacvalue