Goal:
  
  A : Type
  P : nat → A → A → Type
  Q : A → Type
  hd : A
  tl : list A
  i : nat
  hd' : A
  p : P i hd hd'
  X : Q hd
  X0 : All Q tl
  ============================
   (Q hd)


DEBUG:Going to execute:
match reverse goal with
           | |- ?X1 => <Coq.Init.Tauto.is_unit_or_eq> flags X1; constructor 1
           | H:?X1 |- _ => <Coq.Init.Tauto.is_empty> flags X1; elim H
           | _ => Ltac.assumption
           end