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


DEBUG:Going to execute:
<Coq.Init.Tauto.is_conj> flags X1; split
Level 2: evaluation returns
<coq-core.plugins.tauto::flatten_contravariant_disj@0>
where
tauto_flags := 
of type
tauto_flags
id := P
of type
constr
X2 := elt -> Prop
of type
constr
X1 := elt
of type
constr of type tacvalue

Level 2: Backtrace:

Tactic failure.
Level 2: Backtrace:

Tactic failure.
Level 1: Backtrace:

Tactic failure.