Goal:
  
  A : Type
  B : Type
  P : B → A → A → Type
  Q : A → Type
  hd : A
  tl : list A
  b : B
  bs : list B
  tl' : list A
  X : OnOne2All P bs tl tl'
  X0 : Q hd
  X1 : All Q tl
  X2 : OnOne2All (λ (i : B) (x y : A), P i x y × Q x) bs tl tl'
  ============================
   (OnOne2All (λ (i : B) (x y : A), P i x y × Q x) bs tl tl')


DEBUG:Going to execute:
<Coq.Init.Tauto.is_unit_or_eq> flags X1; Ltac.cut X2;
            [ intro; clear id
            | Ltac.cut X1; [ exact id | constructor 1; fail ] ]
Level 0: Backtrace:

P is used in conclusion.
Level 0: Backtrace:

P is used in conclusion.
Level 0: Backtrace:

P is used in conclusion.
Level 0: Backtrace:

P is used in conclusion.
Level 0: Backtrace:

P is used in conclusion.
Level 1: Backtrace:

P is used in conclusion.
Level 0: Backtrace:

P is used in conclusion.
Level 2: Backtrace:

Not convertible.
Level 2: Backtrace:

Not convertible.
Level 2: Backtrace:

Not convertible.
Level 1: Backtrace:

Not convertible.