Goal:
  
  A : Type
  P : nat → A → Type
  p : nat → A → bool
  Hp : ∀ (i : nat) (x : A), reflectT (P i x) (p i x)
  n : nat
  hd : A
  tl : list A
  p0 : P n hd
  X : Alli P (S n) tl
  IHX : is_true (alli p (S n) tl)
  p1 : P n hd
  ============================
   (is_true true)


DEBUG:Going to execute:
(solve [ do_atom | use_hyps; do_ccl ]) ||
             fail "Cannot solve this goal"