proposition: Lemma iipc2_weakening {Gamma Gamma' t} : incl Gamma Gamma' -> iipc2 Gamma t -> iipc2 Gamma' t.
proof: Proof. by move=> /incl_nth_error [?] /typing_ren_term' H [?] /H /iipc2I. Qed.
imports: List Lia Undecidability.SystemF.SysF Undecidability.SystemF.Autosubst.syntax Undecidability.SystemF.Util(Facts poly_type_facts typing_facts) ssreflect ssrbool ssrfun