Goal:
  
  A : Type
  P : nat → A → A → Type
  i : nat
  hd : A
  tl : list A
  tl' : list A
  h : OnOne2i P (S i) tl tl'
  i' : nat
  x : A
  y : A
  u : list A
  v : list A
  p : P i' x y × tl = u ++ x :: v ∧ tl' = u ++ y :: v
  ============================
   (P i' x y
    × hd :: tl = (hd :: u) ++ x :: v ∧ hd :: tl' = (hd :: u) ++ y :: v)


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 := eauto
     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 := eauto
     of type
     tacvalue
of type
tacvalue of type tacvalue