Goal:
  
  A : Type
  P : list A → list A → A → A → Type
  H1' : list A
  H1 : list A
  H : All2_fold P H1' H1
  ============================
   (∀ (H := CoreTactics.block) (Γ : list A),
      {| pr1 := Γ; pr2 := Γ |} = {| pr1 := H1'; pr2 := H1 |}
      → let H0 := CoreTactics.block in
        let H1 := CoreTactics.block in
        All_fold (λ (Γ0 : list A) (d : A), P Γ0 Γ0 d d) Γ)


DEBUG:Going to execute:
fun tac p =>
             let ty := type of p in
             let eliminator := eval simpl in DepElim.elim in
             tac p eliminator