Goal:
    A : Type  P : nat → A → Type  Q : nat → A → Type  l : list A  n : nat
  ============================
   (Alli P n l → Alli (λ (n : nat) (x : A), P n x → Q n x) n l → Alli Q n l)


DEBUG:Going to execute:
induction 1; inversion 1; constructor