Goal:
    x : t  y : t  z : t  H0 : lt z y  H : compare z x = Lt
  ============================
   (Gt = Gt -> CompOpp Lt = Gt)


DEBUG:Going to execute:
trivial; hnf; intros; (solve
            [ do
            ![ solve
             [ trivial | apply : eq_sym ; trivial ]
             | discriminate
             | contradiction
             | Ltac.split ]
            | case not_locked_false_eq_true; Ltac.assumption
            | match goal with
              | H:~ _ |- _ => solve [ case H; trivial ]
              end ])