proposition: Lemma iipc2_var_InI {Gamma t} : In t Gamma -> iipc2 Gamma t.
proof: Proof. move=> /In_nth_error [?] /typing_var ?. eexists. by eassumption. Qed.
imports: List Lia Undecidability.SystemF.SysF Undecidability.SystemF.Autosubst.syntax Undecidability.SystemF.Util(Facts poly_type_facts typing_facts) ssreflect ssrbool ssrfun