Goal:
    A : Type  P : A → Type  Q : A → Type  Hl' : All Q []
  ============================
   (All (λ x : A, P x × Q x) [])


DEBUG:Going to execute:
DepElim.is_introduced H; CoreTactics.block_goal;
            CoreTactics.revert_until H; CoreTactics.block_goal