Goal:
    A : Type  n : nat  P : A → bool  d : A  H : is_true true  H0 : S n < 0
  ============================
   (∃ x : A, d = x ∧ P x)


DEBUG:Going to execute:
fun H =>
             match type of H with
             | _ ∧ _ => exact H || destruct_hyp H
             | _ * _ => exact H || destruct_hyp H
             | _ => try (solve [ inversion H ])
             end