Goal:
  
  A : Type
  P : A → Type
  Q : A → Type
  x : A
  l : list A
  p : P x
  Hl : All P l
  Hl' : All Q (x :: l)
  IHHl : All Q l → All (λ x : A, P x × Q x) l
  ============================
   (All (λ x : A, P x × Q x) (x :: l))


DEBUG:Going to execute:
DepElim.depelim H
Level 3: evaluation returns
DepElim.do_depelim_nosimpl tac H; DepElim.simpl_dep_elim;
 CoreTactics.unblock_goal
where
tac := fun hyp => DepElim.do_case hyp
       where
       id := Hl'
       of type
       constr
of type
tacvalue
H := Hl'
of type
constr of type tacvalue

Level 2: evaluation returns
DepElim.do_depelim_nosimpl tac H; DepElim.simpl_dep_elim;
 CoreTactics.unblock_goal
where
tac := fun hyp => DepElim.do_case hyp
       where
       id := Hl'
       of type
       constr
of type
tacvalue
H := Hl'
of type
constr of type tacvalue

Level 1: evaluation returns
DepElim.do_depelim_nosimpl tac H; DepElim.simpl_dep_elim;
 CoreTactics.unblock_goal
where
tac := fun hyp => DepElim.do_case hyp
       where
       id := Hl'
       of type
       constr
of type
tacvalue
H := Hl'
of type
constr of type tacvalue