Module: Mathlib.Topology.Algebra.InfiniteSum.TsumUniformlyOn

Goal state before:
pp: case succ
ι : Type u_1
𝕜 : Type u_2
F : Type u_3
inst✝³ : NontriviallyNormedField 𝕜
inst✝² : IsRCLikeNormedField 𝕜
inst✝¹ : NormedAddCommGroup F
inst✝ : NormedSpace 𝕜 F
s : Set 𝕜
f : ι → 𝕜 → F
hs : IsOpen[PseudoMetricSpace.toUniformSpace.toTopologicalSpace] s
hsum : ∀ t ∈ s, Summable fun n ↦ f n t
m : ℕ
hm :
  ∀ {x : 𝕜},
    x ∈ s →
      (∀ (k : ℕ), 1 ≤ k → k ≤ m → SummableLocallyUniformlyOn (fun n ↦ iteratedDerivWithin k (fun z ↦ f n z) s) s) →
        (∀ (n : ι) (k : ℕ) (r : 𝕜), k ≤ m → r ∈ s → DifferentiableAt 𝕜 (iteratedDerivWithin k (fun z ↦ f n z) s) r) →
          iteratedDerivWithin m (fun z ↦ ∑' (n : ι), f n z) s x = ∑' (n : ι), iteratedDerivWithin m (f n) s x
x : 𝕜
hx : x ∈ s
h : ∀ (k : ℕ), 1 ≤ k → k ≤ m + 1 → SummableLocallyUniformlyOn (fun n ↦ iteratedDerivWithin k (fun z ↦ f n z) s) s
hf2 : ∀ (n : ι) (k : ℕ) (r : 𝕜), k ≤ m + 1 → r ∈ s → DifferentiableAt 𝕜 (iteratedDerivWithin k (fun z ↦ f n z) s) r
⊢ derivWithin (iteratedDerivWithin m (fun z ↦ ∑' (n : ι), f n z) s) s x =
    ∑' (n : ι), derivWithin (iteratedDerivWithin m (f n) s) s x

Tactic:
rw [← derivWithin_tsum hs hx _ _ (fun n r hr ↦ hf2 n m r (by lia) hr)]

Goal state after:
case succ
ι : Type u_1
𝕜 : Type u_2
F : Type u_3
inst✝³ : NontriviallyNormedField 𝕜
inst✝² : IsRCLikeNormedField 𝕜
inst✝¹ : NormedAddCommGroup F
inst✝ : NormedSpace 𝕜 F
s : Set 𝕜
f : ι → 𝕜 → F
hs : IsOpen[PseudoMetricSpace.toUniformSpace.toTopologicalSpace] s
hsum : ∀ t ∈ s, Summable fun n ↦ f n t
m : ℕ
hm :
  ∀ {x : 𝕜},
    x ∈ s →
      (∀ (k : ℕ), 1 ≤ k → k ≤ m → SummableLocallyUniformlyOn (fun n ↦ iteratedDerivWithin k (fun z ↦ f n z) s) s) →
        (∀ (n : ι) (k : ℕ) (r : 𝕜), k ≤ m → r ∈ s → DifferentiableAt 𝕜 (iteratedDerivWithin k (fun z ↦ f n z) s) r) →
          iteratedDerivWithin m (fun z ↦ ∑' (n : ι), f n z) s x = ∑' (n : ι), iteratedDerivWithin m (f n) s x
x : 𝕜
hx : x ∈ s
h : ∀ (k : ℕ), 1 ≤ k → k ≤ m + 1 → SummableLocallyUniformlyOn (fun n ↦ iteratedDerivWithin k (fun z ↦ f n z) s) s
hf2 : ∀ (n : ι) (k : ℕ) (r : 𝕜), k ≤ m + 1 → r ∈ s → DifferentiableAt 𝕜 (iteratedDerivWithin k (fun z ↦ f n z) s) r
⊢ derivWithin (iteratedDerivWithin m (fun z ↦ ∑' (n : ι), f n z) s) s x =
    derivWithin (fun z ↦ ∑' (n : ι), iteratedDerivWithin m (fun z ↦ f n z) s z) s x

ι : Type u_1
𝕜 : Type u_2
F : Type u_3
inst✝³ : NontriviallyNormedField 𝕜
inst✝² : IsRCLikeNormedField 𝕜
inst✝¹ : NormedAddCommGroup F
inst✝ : NormedSpace 𝕜 F
s : Set 𝕜
f : ι → 𝕜 → F
hs : IsOpen[PseudoMetricSpace.toUniformSpace.toTopologicalSpace] s
hsum : ∀ t ∈ s, Summable fun n ↦ f n t
m : ℕ
hm :
  ∀ {x : 𝕜},
    x ∈ s →
      (∀ (k : ℕ), 1 ≤ k → k ≤ m → SummableLocallyUniformlyOn (fun n ↦ iteratedDerivWithin k (fun z ↦ f n z) s) s) →
        (∀ (n : ι) (k : ℕ) (r : 𝕜), k ≤ m → r ∈ s → DifferentiableAt 𝕜 (iteratedDerivWithin k (fun z ↦ f n z) s) r) →
          iteratedDerivWithin m (fun z ↦ ∑' (n : ι), f n z) s x = ∑' (n : ι), iteratedDerivWithin m (f n) s x
x : 𝕜
hx : x ∈ s
h : ∀ (k : ℕ), 1 ≤ k → k ≤ m + 1 → SummableLocallyUniformlyOn (fun n ↦ iteratedDerivWithin k (fun z ↦ f n z) s) s
hf2 : ∀ (n : ι) (k : ℕ) (r : 𝕜), k ≤ m + 1 → r ∈ s → DifferentiableAt 𝕜 (iteratedDerivWithin k (fun z ↦ f n z) s) r
⊢ ∀ y ∈ s, Summable fun n ↦ iteratedDerivWithin m (fun z ↦ f n z) s y

ι : Type u_1
𝕜 : Type u_2
F : Type u_3
inst✝³ : NontriviallyNormedField 𝕜
inst✝² : IsRCLikeNormedField 𝕜
inst✝¹ : NormedAddCommGroup F
inst✝ : NormedSpace 𝕜 F
s : Set 𝕜
f : ι → 𝕜 → F
hs : IsOpen[PseudoMetricSpace.toUniformSpace.toTopologicalSpace] s
hsum : ∀ t ∈ s, Summable fun n ↦ f n t
m : ℕ
hm :
  ∀ {x : 𝕜},
    x ∈ s →
      (∀ (k : ℕ), 1 ≤ k → k ≤ m → SummableLocallyUniformlyOn (fun n ↦ iteratedDerivWithin k (fun z ↦ f n z) s) s) →
        (∀ (n : ι) (k : ℕ) (r : 𝕜), k ≤ m → r ∈ s → DifferentiableAt 𝕜 (iteratedDerivWithin k (fun z ↦ f n z) s) r) →
          iteratedDerivWithin m (fun z ↦ ∑' (n : ι), f n z) s x = ∑' (n : ι), iteratedDerivWithin m (f n) s x
x : 𝕜
hx : x ∈ s
h : ∀ (k : ℕ), 1 ≤ k → k ≤ m + 1 → SummableLocallyUniformlyOn (fun n ↦ iteratedDerivWithin k (fun z ↦ f n z) s) s
hf2 : ∀ (n : ι) (k : ℕ) (r : 𝕜), k ≤ m + 1 → r ∈ s → DifferentiableAt 𝕜 (iteratedDerivWithin k (fun z ↦ f n z) s) r
⊢ SummableLocallyUniformlyOn (fun n ↦ derivWithin (fun z ↦ iteratedDerivWithin m (fun z ↦ f n z) s z) s) s