Goal:
    A : Type  P : A → Type  f : A → A  H : ∀ x : A, P x → f x = x
  ============================
   ([] = [])


DEBUG:Going to execute:
match reverse goal with
           | |- ?X1 => <Coq.Init.Tauto.is_unit_or_eq> flags X1; constructor 1
           | H:?X1 |- _ => <Coq.Init.Tauto.is_empty> flags X1; elim H
           | _ => Ltac.assumption
           end