Definition ordinal_finMixin :=
  Eval hnf in UniqFinMixin ord_enum_uniq mem_ord_enum.Canonical ordinal_finType := Eval hnf in FinType ordinal ordinal_finMixin.Definition widen_ord n m le_n_m i := Ordinal (@widen_ord_proof n m i le_n_m).Definition cast_ord n m eq_n_m i := Ordinal (@cast_ord_proof n m i eq_n_m).

Lemma cast_ordK n1 n2 eq_n : cancel (@cast_ord n1 n2 eq_n) (cast_ord (esym eq_n)).