Goal:
  
  A : Type
  P : nat → A → Type
  Q : nat → A → Type
  n : nat
  hd : A
  tl : list A
  p : P n hd
  X : Alli P (S n) tl
  IHX : Alli (λ (n : nat) (x : A), P n x → Q n x) (S n) tl → Alli Q (S n) tl
  X0 : Alli (λ (n : nat) (x : A), P n x → Q n x) n (hd :: tl)
  hd0 : A
  tl0 : list A
  X1 : P n hd → Q n hd
  X2 : Alli (λ (n : nat) (x : A), P n x → Q n x) (S n) tl
  H0 : hd0 = hd
  H1 : tl0 = tl
  ============================
   (Q n hd)


DEBUG:Going to execute:
F x2 x1 x0
Level 0: Backtrace:

P is used in hypothesis p.
Level 0: Backtrace:

P is used in hypothesis p.
Level 0: Backtrace:

P is used in hypothesis p.
Level 0: Backtrace:

P is used in hypothesis p.
Level 0: Backtrace:

P is used in hypothesis p.
Level 1: Backtrace:

P is used in hypothesis p.
Level 0: Backtrace:

P is used in hypothesis p.