Goal:
  
  A : Type
  B : Type
  n : nat
  t : A
  P : B → A → A → Type
  b : B
  bs : list B
  hd : A
  hd' : A
  tl : list A
  p : P b hd hd'
  e : #|bs| = #|tl|
  hnth : nth_error tl n = Some t
  ============================
   (nth_error tl n = Some t
    × (t = t) + (∑ i' : B, nth_error bs n = Some i' × P i' t t))


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 := auto
     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 := auto
     of type
     tacvalue
of type
tacvalue of type tacvalue