proposition: Fact erase_subst_term_var {P σ} : erase (subst_term σ var P) = erase P.
proof: Proof. elim: P σ; move=> /= *; rewrite ?subst_term_up_term_term_var ?subst_term_up_poly_type_term_var; by congruence. 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