Goal:
  
  A : Type
  P : nat → A → Type
  n : nat
  n0 : nat
  hd : A
  tl : list A
  p : P (n + n0) hd
  X : Alli (λ x : nat, P (n + x)) (S n0) tl
  IHX : Alli P (S (n + n0)) tl
  ============================
   (Alli P (S (n + n0)) tl)


DEBUG:Going to execute:
let rec do_ccl :=
            try do_atom; repeat (do_intro; try do_atom); try arith_congr;
             (solve [ split; do_ccl ])
           in
           (solve [ do_atom | use_hyps; do_ccl ]) ||
             fail "Cannot solve this goal"