Goal:
  
  A : Type
  P : A → Prop
  Q : A → Prop
  p : A → bool
  Hp : ∀ x : A, Q x → reflect (P x) (p x)
  HP1 : list A
  ============================
   (Forall P HP1
    → [] = HP1
      → let H := CoreTactics.block in
        let H0 := CoreTactics.block in forallb p [] = true)


DEBUG:Going to execute:
intros p