∀ {R : Type u_2} [inst : CommRing R] {τ : Type u_3} {S : Type u_4} [inst_1 : CommRing S] [inst_2 : Algebra R S]
  {a : MvPowerSeries τ S},
  PowerSeries.HasSubst a → ∀ (p : Polynomial R), PowerSeries.subst a ↑p = (Polynomial.aeval a) p