Proof using.
intros t H; red in |- *.
intros a t1 t2 H0 H1 H2; apply (H a t1 t2); auto.
inversion H0; auto.
Qed.

(* A right has distinct leaves if its subtree has it *)
Theorem distinct_pbleaves_pbright :
forall t, distinct_pbleaves t -> distinct_pbleaves (pbright t).