∀ {X : Type u_1} {n : Type u_5} {R : Type u_8} [inst : AddCommMonoid R] [inst_1 : TopologicalSpace R]
  {L : SummationFilter X} [inst_2 : DecidableEq n] {f : X → n → R} {a : n → R},
  HasSum f a L → HasSum (fun x => Matrix.diagonal (f x)) (Matrix.diagonal a) L