Goal:
  
  A : Type
  P : list A → list A → A → A → Type
  d : A
  Γ : list A
  H : All2_fold P Γ Γ
  p : P Γ Γ d d
  IHAll2_fold : All_fold (λ (Γ : list A) (d : A), P Γ Γ d d) Γ
  ============================
   (let H := CoreTactics.block in
    All_fold (λ (Γ : list A) (d : A), P Γ Γ d d) (d :: Γ))


DEBUG:Going to execute:
match goal with
           | |- let _ := CoreTactics.block in _ => intros _
           | |- _ => try (intro; CoreTactics.intros_until_block)
           end