Goal:
  
  A : Type
  P : list A → A → Type
  Q : list A → list A → A → A → Type
  Δ : list A
  d : A
  Γ : list A
  hlen : #|d :: Γ| = #|Δ|
  ha : All_fold P Γ
  p : P Γ d
  hb : All_fold P Δ
  ============================
   (let H := CoreTactics.block in
    (∀ (Δ Δ' : list A) (x y : A),
       All_fold P Δ
       → All_fold P Δ' → All2_fold Q Δ Δ' → P Δ x → P Δ' y → Q Δ Δ' x y)
    → (∀ Δ : list A, #|Γ| = #|Δ| → All_fold P Δ → All2_fold Q Γ Δ)
      → let H0 := CoreTactics.block in All2_fold Q (d :: Γ) Δ)


DEBUG:Going to execute:
try simpl in H; DepElim.simplify_equations_in H
DEBUG LTAC Evaluated term: (let H := CoreTactics.block in
                            (∀ (Δ Δ' : list A) (x y : A),
                               All_fold P Δ
                               → All_fold P Δ'
                                 → All2_fold Q Δ Δ'
                                   → P Δ x → P Δ' y → Q Δ Δ' x y)
                            → (∀ Δ : list A,
                                 #|Γ| = #|Δ| → All_fold P Δ → All2_fold Q Γ Δ)
                              → let H0 := CoreTactics.block in
                                All2_fold Q (d :: Γ) Δ)