(M : Type u_1) →
  {α : Type u_2} →
    [inst : Group M] →
      [inst_1 : MulAction M α] →
        {s t : Set α} →
          (hst : s = t) →
            have φ := MulEquiv.subgroupCongr ⋯;
            ↥(SubMulAction.ofFixingSubgroup M s) →ₑ[⇑φ] ↥(SubMulAction.ofFixingSubgroup M t)