Goal:
  
  A : Type
  P : nat → A → A → Type
  Q : nat → A → A → Type
  i : nat
  hd : A
  tl : list A
  tl' : list A
  H : OnOne2i P (S i) tl tl'
  HPQ : ∀ (i : nat) (x y : A), P i x y → ∑ z : A, Q i x z × Q i y z
  r : list A
  o : OnOne2i Q (S i) tl r
  o0 : OnOne2i Q (S i) tl' r
  ============================
   (OnOne2i Q i (hd :: tl) (hd :: r) × OnOne2i Q i (hd :: tl') (hd :: r))


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 := constructor
     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 := constructor
     of type
     tacvalue
of type
tacvalue of type tacvalue