fact: Definition gen_constructor args num i := it lam args (it lam num (it_i (fun n s => L.app s #(n + num)) args (var (num - i - 1)))).
imports: Ascii String Undecidability.L(Util.L_facts) MetaCoq(Template.All Template.Checker) Undecidability.Shared.Libs.PSL.Base MetaCoq.Utils.bytestring