Goal:
  
  P : elt -> elt -> Prop
  s : t
  H : forall v1 v2 : elt, In v1 s -> In v2 s -> P v1 v2
  x : elt
  H0 : In x s
  ============================
   (forall x0 : elt, In x0 s -> P x x0)


DEBUG:Going to execute:
<Coq.Init.Tauto.find_cut>
            ltac:(fun id0 id1 X2 =>
                    assert X2; [ exact (id0 id1) | clear id0 ])
Level 3: evaluation returns
<coq-core.plugins.tauto::is_disj@0>
where
tauto_flags := 
of type
tauto_flags
X1 := In x s
of type
constr of type tacvalue

Level 3: Backtrace:

Tactic failure.
Level 3: Backtrace:

Tactic failure.
Level 2: Backtrace:

Tactic failure.
Level 2: Backtrace:

Tactic failure.
Level 2: Backtrace:

Tactic failure.
Level 2: Backtrace:

Tactic failure.