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


DEBUG:Going to execute:
match goal with
           | |- _ -> _ => intro; t_tauto_intuit
           | |- _ => t_reduce; t_solver
           end || t_solver
Level 3: evaluation returns
<coq-core.plugins.tauto::is_disj@0>
where
tauto_flags := 
of type
tauto_flags
X1 := forall v2 : elt, In v1 s -> In v2 s -> P v1 v2
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 1: Backtrace:

Tactic failure.