Goal:
  
  A : Type
  B : Type
  k : nat
  Q : nat → A → Type
  R : nat → A → B → Type
  l : list A
  l' : list B
  n : nat
  q : Alli Q n []
  ============================
   (All2i (λ (i : nat) (x : A) (y : B), Q i x × R i x y) n [] [])


DEBUG:Going to execute:
DepElim.do_intros H; DepElim.generalize_by_eqs H
Level 1: evaluation returns
DepElim.do_intros H; DepElim.generalize_by_eqs H; tac H
where
tac := fun hyp => DepElim.do_case hyp
       where
       id := q
       of type
       intropattern
of type
tacvalue
H := q
of type
intropattern of type tacvalue