Goal:
  
  A : Type
  B : Type
  P : B → A → A → Type
  Q : B → A → A → Type
  b : B
  bs : list B
  hd : A
  tl : list A
  tl' : list A
  H : OnOne2All P bs tl tl'
  HPQ : ∀ (i : B) (x y : A), P i x y → ∑ z : A, Q i x z × Q i y z
  r : list A
  o : OnOne2All Q bs tl r
  o0 : OnOne2All Q bs tl' r
  ============================
   (OnOne2All Q (b :: bs) (hd :: tl) (hd :: r))


DEBUG:Going to execute:
F x2 x1 x0
Level 2: evaluation returns
<coq-core.plugins.tauto::find_cut@0>
where
k := fun id0 id1 X2 => assert X2; [ exact (id0 id1) | clear id0 ]
     where
     flags := 
     of type
     tauto_flags
of type
tacvalue of type tacvalue