proposition: Lemma subst_term_up_poly_type_term_var {σ t}: subst_term σ (up_poly_type_term var) t = subst_term σ var t.
proof: Proof. apply: ext_term; [done | by case]. Qed.
imports: List Lia Undecidability.SystemF.SysF Undecidability.SystemF.Autosubst.syntax Undecidability.SystemF.Autosubst.unscoped Undecidability.SystemF.Util(Facts poly_type_facts pure_term_facts) ssreflect ssrbool ssrfun