proposition: Fact ren_poly_type_id {t}: ren_poly_type id t = t.
proof: Proof. rewrite -[RHS]subst_poly_type_poly_var. by apply: rinst_inst_poly_type. Qed.
imports: List Lia Undecidability.SystemF.SysF Undecidability.SystemF.Autosubst.syntax Undecidability.SystemF.Autosubst.unscoped Undecidability.SystemF.Util.Facts ssreflect ssrbool ssrfun