-- Mathlib/Analysis/BoxIntegral/Box/SubboxInduction.lean
theorem subbox_induction_on' {p : Box ι → Prop} (I : Box ι)
    (H_ind : ∀ J ≤ I, (∀ s, p (splitCenterBox J s)) → p J)
    (H_nhds : ∀ z ∈ Box.Icc I, ∃ U ∈ 𝓝[Box.Icc I] z, ∀ J ≤ I, ∀ (m : ℕ), z ∈ Box.Icc J →
      Box.Icc J ⊆ U → (∀ i, J.upper i - J.lower i = (I.upper i - I.lower i) / 2 ^ m) → p J) :
    p I

Proof state:
ι : Type u_1
p : Box ι → Prop
I : Box ι
H_nhds :
  ∀ z ∈ Box.Icc I,
    ∃ U ∈ 𝓝[Box.Icc I] z,
      ∀ J ≤ I,
        ∀ (m : ℕ),
          z ∈ Box.Icc J → Box.Icc J ⊆ U → (∀ (i : ι), J.upper i - J.lower i = (I.upper i - I.lower i) / 2 ^ m) → p J
J : ℕ → Box ι
hJmono : Antitone J
hJle : ∀ (m : ℕ), J m ≤ I
hJp : ∀ (m : ℕ), ¬p (J m)
hJsub : ∀ (m : ℕ) (i : ι), (J m).upper i - (J m).lower i = (I.upper i - I.lower i) / 2 ^ m
h0 : J 0 = I
z : ι → ℝ := ⨆ m, (J m).lower
hzJ : ∀ (m : ℕ), z ∈ Box.Icc (J m)
hJl_mem : ∀ (m : ℕ), (J m).lower ∈ Box.Icc I
hJu_mem : ∀ (m : ℕ), (J m).upper ∈ Box.Icc I
hJuz : Tendsto (fun m => (J m).upper) atTop (𝓝 z)
hJlz : Tendsto (fun m => (J m).lower) atTop (𝓝[Icc I.lower I.upper] z)
⊢ False

Tactic:
replace hJuz : Tendsto (fun m ↦ (J m).upper) atTop (𝓝[Icc I.lower I.upper] z) :=
  tendsto_nhdsWithin_of_tendsto_nhds_of_eventually_within _ hJuz (Eventually.of_forall hJu_mem)

Result:
ι : Type u_1
p : Box ι → Prop
I : Box ι
H_nhds :
  ∀ z ∈ Box.Icc I,
    ∃ U ∈ 𝓝[Box.Icc I] z,
      ∀ J ≤ I,
        ∀ (m : ℕ),
          z ∈ Box.Icc J → Box.Icc J ⊆ U → (∀ (i : ι), J.upper i - J.lower i = (I.upper i - I.lower i) / 2 ^ m) → p J
J : ℕ → Box ι
hJmono : Antitone J
hJle : ∀ (m : ℕ), J m ≤ I
hJp : ∀ (m : ℕ), ¬p (J m)
hJsub : ∀ (m : ℕ) (i : ι), (J m).upper i - (J m).lower i = (I.upper i - I.lower i) / 2 ^ m
h0 : J 0 = I
z : ι → ℝ := ⨆ m, (J m).lower
hzJ : ∀ (m : ℕ), z ∈ Box.Icc (J m)
hJl_mem : ∀ (m : ℕ), (J m).lower ∈ Box.Icc I
hJu_mem : ∀ (m : ℕ), (J m).upper ∈ Box.Icc I
hJlz : Tendsto (fun m => (J m).lower) atTop (𝓝[Icc I.lower I.upper] z)
hJuz : Tendsto (fun m => (J m).upper) atTop (𝓝[Icc I.lower I.upper] z)
⊢ False

Proof state:
ι : Type u_1
p : Box ι → Prop
I : Box ι
H_nhds :
  ∀ z ∈ Box.Icc I,
    ∃ U ∈ 𝓝[Box.Icc I] z,
      ∀ J ≤ I,
        ∀ (m : ℕ),
          z ∈ Box.Icc J → Box.Icc J ⊆ U → (∀ (i : ι), J.upper i - J.lower i = (I.upper i - I.lower i) / 2 ^ m) → p J
hpI : ¬p I
s : Box ι → Set ι
hs : ∀ J ≤ I, ¬p J → ¬p (J.splitCenterBox (s J))
J : ℕ → Box ι := fun m => (fun J => J.splitCenterBox (s J))^[m] I
J_succ : ∀ (m : ℕ), J (m + 1) = (J m).splitCenterBox (s (J m))
⊢ False

Tactic:
have hJmono : Antitone J :=
  antitone_nat_of_succ_le fun n ↦ by simpa [J_succ] using splitCenterBox_le _ _

Result:
ι : Type u_1
p : Box ι → Prop
I : Box ι
H_nhds :
  ∀ z ∈ Box.Icc I,
    ∃ U ∈ 𝓝[Box.Icc I] z,
      ∀ J ≤ I,
        ∀ (m : ℕ),
          z ∈ Box.Icc J → Box.Icc J ⊆ U → (∀ (i : ι), J.upper i - J.lower i = (I.upper i - I.lower i) / 2 ^ m) → p J
hpI : ¬p I
s : Box ι → Set ι
hs : ∀ J ≤ I, ¬p J → ¬p (J.splitCenterBox (s J))
J : ℕ → Box ι := fun m => (fun J => J.splitCenterBox (s J))^[m] I
J_succ : ∀ (m : ℕ), J (m + 1) = (J m).splitCenterBox (s (J m))
hJmono : Antitone J
⊢ False

Proof state:
ι : Type u_1
p : Box ι → Prop
I : Box ι
H_nhds :
  ∀ z ∈ Box.Icc I,
    ∃ U ∈ 𝓝[Box.Icc I] z,
      ∀ J ≤ I,
        ∀ (m : ℕ),
          z ∈ Box.Icc J → Box.Icc J ⊆ U → (∀ (i : ι), J.upper i - J.lower i = (I.upper i - I.lower i) / 2 ^ m) → p J
hpI : ¬p I
H_ind : ∀ J ≤ I, ¬p J → ∃ x, ¬p (J.splitCenterBox x)
⊢ False

Tactic:
choose! s hs using H_ind

Result:
ι : Type u_1
p : Box ι → Prop
I : Box ι
H_nhds :
  ∀ z ∈ Box.Icc I,
    ∃ U ∈ 𝓝[Box.Icc I] z,
      ∀ J ≤ I,
        ∀ (m : ℕ),
          z ∈ Box.Icc J → Box.Icc J ⊆ U → (∀ (i : ι), J.upper i - J.lower i = (I.upper i - I.lower i) / 2 ^ m) → p J
hpI : ¬p I
s : Box ι → Set ι
hs : ∀ J ≤ I, ¬p J → ¬p (J.splitCenterBox (s J))
⊢ False

Proof state:
case intro.intro
ι : Type u_1
p : Box ι → Prop
I : Box ι
H_nhds :
  ∀ z ∈ Box.Icc I,
    ∃ U ∈ 𝓝[Box.Icc I] z,
      ∀ J ≤ I,
        ∀ (m : ℕ),
          z ∈ Box.Icc J → Box.Icc J ⊆ U → (∀ (i : ι), J.upper i - J.lower i = (I.upper i - I.lower i) / 2 ^ m) → p J
J : ℕ → Box ι
hJmono : Antitone J
hJle : ∀ (m : ℕ), J m ≤ I
hJp : ∀ (m : ℕ), ¬p (J m)
hJsub : ∀ (m : ℕ) (i : ι), (J m).upper i - (J m).lower i = (I.upper i - I.lower i) / 2 ^ m
h0 : J 0 = I
z : ι → ℝ := ⨆ m, (J m).lower
hzJ : ∀ (m : ℕ), z ∈ Box.Icc (J m)
hJl_mem : ∀ (m : ℕ), (J m).lower ∈ Box.Icc I
hJu_mem : ∀ (m : ℕ), (J m).upper ∈ Box.Icc I
hJlz : Tendsto (fun m => (J m).lower) atTop (𝓝[Icc I.lower I.upper] z)
hJuz : Tendsto (fun m => (J m).upper) atTop (𝓝[Icc I.lower I.upper] z)
U : Set (ι → ℝ)
hUz : U ∈ 𝓝[Box.Icc I] z
hU :
  ∀ J ≤ I,
    ∀ (m : ℕ),
      z ∈ Box.Icc J → Box.Icc J ⊆ U → (∀ (i : ι), J.upper i - J.lower i = (I.upper i - I.lower i) / 2 ^ m) → p J
⊢ False

Tactic:
rcases (tendsto_lift'.1 (hJlz.Icc hJuz) U hUz).exists with ⟨m, hUm⟩

Result:
case intro.intro.intro
ι : Type u_1
p : Box ι → Prop
I : Box ι
H_nhds :
  ∀ z ∈ Box.Icc I,
    ∃ U ∈ 𝓝[Box.Icc I] z,
      ∀ J ≤ I,
        ∀ (m : ℕ),
          z ∈ Box.Icc J → Box.Icc J ⊆ U → (∀ (i : ι), J.upper i - J.lower i = (I.upper i - I.lower i) / 2 ^ m) → p J
J : ℕ → Box ι
hJmono : Antitone J
hJle : ∀ (m : ℕ), J m ≤ I
hJp : ∀ (m : ℕ), ¬p (J m)
hJsub : ∀ (m : ℕ) (i : ι), (J m).upper i - (J m).lower i = (I.upper i - I.lower i) / 2 ^ m
h0 : J 0 = I
z : ι → ℝ := ⨆ m, (J m).lower
hzJ : ∀ (m : ℕ), z ∈ Box.Icc (J m)
hJl_mem : ∀ (m : ℕ), (J m).lower ∈ Box.Icc I
hJu_mem : ∀ (m : ℕ), (J m).upper ∈ Box.Icc I
hJlz : Tendsto (fun m => (J m).lower) atTop (𝓝[Icc I.lower I.upper] z)
hJuz : Tendsto (fun m => (J m).upper) atTop (𝓝[Icc I.lower I.upper] z)
U : Set (ι → ℝ)
hUz : U ∈ 𝓝[Box.Icc I] z
hU :
  ∀ J ≤ I,
    ∀ (m : ℕ),
      z ∈ Box.Icc J → Box.Icc J ⊆ U → (∀ (i : ι), J.upper i - J.lower i = (I.upper i - I.lower i) / 2 ^ m) → p J
m : ℕ
hUm : Icc (J m).lower (J m).upper ∈ 𝒫 U
⊢ False

Proof state:
ι : Type u_1
p : Box ι → Prop
I : Box ι
H_nhds :
  ∀ z ∈ Box.Icc I,
    ∃ U ∈ 𝓝[Box.Icc I] z,
      ∀ J ≤ I,
        ∀ (m : ℕ),
          z ∈ Box.Icc J → Box.Icc J ⊆ U → (∀ (i : ι), J.upper i - J.lower i = (I.upper i - I.lower i) / 2 ^ m) → p J
J : ℕ → Box ι
hJmono : Antitone J
hJle : ∀ (m : ℕ), J m ≤ I
hJp : ∀ (m : ℕ), ¬p (J m)
hJsub : ∀ (m : ℕ) (i : ι), (J m).upper i - (J m).lower i = (I.upper i - I.lower i) / 2 ^ m
h0 : J 0 = I
z : ι → ℝ := ⨆ m, (J m).lower
hzJ : ∀ (m : ℕ), z ∈ Box.Icc (J m)
hJl_mem : ∀ (m : ℕ), (J m).lower ∈ Box.Icc I
hJu_mem : ∀ (m : ℕ), (J m).upper ∈ Box.Icc I
hJlz : Tendsto (fun m => (J m).lower) atTop (𝓝 z)
hJuz : Tendsto (fun m => (J m).upper) atTop (𝓝 z)
⊢ False

Tactic:
replace hJlz : Tendsto (fun m ↦ (J m).lower) atTop (𝓝[Icc I.lower I.upper] z) :=
  tendsto_nhdsWithin_of_tendsto_nhds_of_eventually_within _ hJlz (Eventually.of_forall hJl_mem)

Result:
ι : Type u_1
p : Box ι → Prop
I : Box ι
H_nhds :
  ∀ z ∈ Box.Icc I,
    ∃ U ∈ 𝓝[Box.Icc I] z,
      ∀ J ≤ I,
        ∀ (m : ℕ),
          z ∈ Box.Icc J → Box.Icc J ⊆ U → (∀ (i : ι), J.upper i - J.lower i = (I.upper i - I.lower i) / 2 ^ m) → p J
J : ℕ → Box ι
hJmono : Antitone J
hJle : ∀ (m : ℕ), J m ≤ I
hJp : ∀ (m : ℕ), ¬p (J m)
hJsub : ∀ (m : ℕ) (i : ι), (J m).upper i - (J m).lower i = (I.upper i - I.lower i) / 2 ^ m
h0 : J 0 = I
z : ι → ℝ := ⨆ m, (J m).lower
hzJ : ∀ (m : ℕ), z ∈ Box.Icc (J m)
hJl_mem : ∀ (m : ℕ), (J m).lower ∈ Box.Icc I
hJu_mem : ∀ (m : ℕ), (J m).upper ∈ Box.Icc I
hJuz : Tendsto (fun m => (J m).upper) atTop (𝓝 z)
hJlz : Tendsto (fun m => (J m).lower) atTop (𝓝[Icc I.lower I.upper] z)
⊢ False