Goal:
  
  A : Type
  P : A → Prop
  Q : A → Prop
  p : A → bool
  x : A
  l : list A
  H : Q x
  HQ : Forall Q l
  Hp : ∀ x : A, Q x → reflect (P x) (p x)
  IHHQ : forallb p l = true → Forall P l
  pa : is_true (p x)
  pl : is_true (forallb p l)
  ============================
   (Forall P (x :: l))


DEBUG:Going to execute:
constructor
DEBUG LTAC Evaluated term: andb_and
DEBUG LTAC Evaluated term: (iffLR (Q:=p x ∧ forallb p l)
                              (andb_and (p x) (forallb p l)) _view_subject_)