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
  ============================
   ((∀ (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 H := CoreTactics.block in All2_fold Q (d :: Γ) Δ)


DEBUG:Going to execute:
CoreTactics.block_goal
Level 14: evaluation returns
idtac of type tacvalue

Level 12: evaluation returns
idtac of type tacvalue

Level 11: evaluation returns
idtac of type tacvalue

Level 9: evaluation returns
idtac of type tacvalue

Level 7: evaluation returns
idtac of type tacvalue

Level 6: evaluation returns
idtac of type tacvalue

Level 4: evaluation returns
idtac of type tacvalue

Level 2: evaluation returns
idtac of type tacvalue

Level 1: evaluation returns
idtac of type tacvalue