proposition: Lemma type_free_db : forall e t T, typ e t T -> free_db (length e) T.
proof: Proof. intros. elim type_case with e t T; intros; auto with coc core arith datatypes. inversion_clear H0. apply typ_free_db with (Srt x); auto with coc core arith datatypes. rewrite H0; auto with coc core arith datatypes. Qed.
imports: Termes Conv MyList