inversion_clear H.
apply typ_wf with T (Srt s); auto with arith pts.
apply typ_wf with T (Srt s); auto with arith pts.
Qed.

Lemma inv_wf_sort :
forall (e : env) (d : decl),
wf (d :: e) -> exists s : sort, typ e (typ_of_decl d) (Srt s).