Goal:
    A : Type  P : A → Type  Q : A → Type  Hl'1 : list A
  ============================
   (All Q Hl'1
    → [] = Hl'1
      → let H := CoreTactics.block in
        let H0 := CoreTactics.block in All (λ x : A, P x × Q x) [])


DEBUG:Going to execute:
intros p