Goal:
    A : Type  P : A → Type  Q : A → Type  Hl' : All Q []
  ============================
   (All (λ x : A, P x × Q x) [])


DEBUG:Going to execute:
fun H =>
             try intros until H; intro_block_id H || intro_block H;
              (try simpl in H; DepElim.simplify_equations_in H)