proposition: Lemma SysF_TYPI Gamma {M} : pure_typable Gamma M -> SysF_TYP M.
proof: Proof. move=> [t] /pure_typing_iff_type_assignment ?. by exists Gamma, t. Qed.
imports: List Lia Undecidability.SystemF.SysF Undecidability.SystemF.Autosubst.syntax Undecidability.SystemF.Util(Facts poly_type_facts pure_term_facts term_facts typing_facts pure_typing_facts pure_typable_prenex) ssreflect ssrbool ssrfun