Goal:
    A : Type  P : nat → A → Type  Q : nat → A → Type  n : nat  l : list A
  ============================
   (Alli P n l → Alli Q n l → Alli (Trel_conj P Q) n l)


DEBUG:Going to execute:
PTRDEBUGTACinduction 1; intros Hq; inv Hq; constructor