/-- A set is eventually carried into any open neighbourhood of its ω-limit:
if `c` is a compact set such that `closure {ϕ t x | t ∈ v, x ∈ s} ⊆ c` for some `v ∈ f`
and `n` is an open neighbourhood of `ω f ϕ s`, then for some `u ∈ f` we have
`closure {ϕ t x | t ∈ u, x ∈ s} ⊆ n`. -/
theorem eventually_closure_subset_of_isCompact_absorbing_of_isOpen_of_omegaLimit_subset' {c : Set β}
    (hc₁ : IsCompact c) (hc₂ : ∃ v ∈ f, closure (image2 ϕ v s) ⊆ c) {n : Set β} (hn₁ : IsOpen n)
    (hn₂ : ω f ϕ s ⊆ n) : ∃ u ∈ f, closure (image2 ϕ u s) ⊆ n := by
  rcases hc₂ with ⟨v, hv₁, hv₂⟩
  let k := closure (image2 ϕ v s)
  have hk : IsCompact (k \ n) :=
    (hc₁.of_isClosed_subset isClosed_closure hv₂).diff hn₁
  let j u := (closure (image2 ϕ (u ∩ v) s))ᶜ
  have hj₁ : ∀ u ∈ f, IsOpen (j u) := fun _ _ ↦ isOpen_compl_iff.mpr isClosed_closure
  have hj₂ : k \ n ⊆ ⋃ u ∈ f, j u := by
    have : ⋃ u ∈ f, j u = ⋃ u : (↥f.sets), j u := biUnion_eq_iUnion _ _
    rw [this, diff_subset_comm, diff_iUnion]
    rw [omegaLimit_eq_iInter_inter _ _ _ hv₁] at hn₂
    simp_rw [diff_compl]
    rw [← inter_iInter]
    exact Subset.trans (inter_subset_right _ _) hn₂
  rcases hk.elim_finite_subcover_image hj₁ hj₂ with ⟨g, hg₁ : ∀ u ∈ g, u ∈ f, hg₂, hg₃⟩
  let w := (⋂ u ∈ g, u) ∩ v
  have hw₂ : w ∈ f := by simpa [*]
  have hw₃ : k \ n ⊆ (closure (image2 ϕ w s))ᶜ := by
    apply Subset.trans hg₃
    simp only [iUnion_subset_iff, compl_subset_compl]
    intros u hu
    mono
    

Proof state:
case h.hs.h₁
τ : Type u_1
α : Type u_2
β : Type u_3
ι : Type u_4
inst✝ : TopologicalSpace β
f : Filter τ
ϕ : τ → α → β
s s₁ s₂ : Set α
c : Set β
hc₁ : IsCompact c
n : Set β
hn₁ : IsOpen n
hn₂ : ω f ϕ s ⊆ n
v : Set τ
hv₁ : v ∈ f
hv₂ : closure (image2 ϕ v s) ⊆ c
k : Set β := closure (image2 ϕ v s)
hk : IsCompact (k \ n)
j : Set τ → Set β := fun u => (closure (image2 ϕ (u ∩ v) s))ᶜ
hj₁ : ∀ u ∈ f, IsOpen (j u)
hj₂ : k \ n ⊆ ⋃ u ∈ f, j u
g : Set (Set τ)
hg₁ : ∀ u ∈ g, u ∈ f
hg₂ : Set.Finite g
hg₃ : k \ n ⊆ ⋃ i ∈ g, j i
w : Set τ := (⋂ u ∈ g, u) ∩ v
hw₂ : w ∈ f
u : Set τ
hu : u ∈ g
⊢ ⋂ u ∈ g, u ⊆ u
case h.hs.h₂
τ : Type u_1
α : Type u_2
β : Type u_3
ι : Type u_4
inst✝ : TopologicalSpace β
f : Filter τ
ϕ : τ → α → β
s s₁ s₂ : Set α
c : Set β
hc₁ : IsCompact c
n : Set β
hn₁ : IsOpen n
hn₂ : ω f ϕ s ⊆ n
v : Set τ
hv₁ : v ∈ f
hv₂ : closure (image2 ϕ v s) ⊆ c
k : Set β := closure (image2 ϕ v s)
hk : IsCompact (k \ n)
j : Set τ → Set β := fun u => (closure (image2 ϕ (u ∩ v) s))ᶜ
hj₁ : ∀ u ∈ f, IsOpen (j u)
hj₂ : k \ n ⊆ ⋃ u ∈ f, j u
g : Set (Set τ)
hg₁ : ∀ u ∈ g, u ∈ f
hg₂ : Set.Finite g
hg₃ : k \ n ⊆ ⋃ i ∈ g, j i
w : Set τ := (⋂ u ∈ g, u) ∩ v
hw₂ : w ∈ f
u : Set τ
hu : u ∈ g
⊢ v ⊆ v
case h.ht
τ : Type u_1
α : Type u_2
β : Type u_3
ι : Type u_4
inst✝ : TopologicalSpace β
f : Filter τ
ϕ : τ → α → β
s s₁ s₂ : Set α
c : Set β
hc₁ : IsCompact c
n : Set β
hn₁ : IsOpen n
hn₂ : ω f ϕ s ⊆ n
v : Set τ
hv₁ : v ∈ f
hv₂ : closure (image2 ϕ v s) ⊆ c
k : Set β := closure (image2 ϕ v s)
hk : IsCompact (k \ n)
j : Set τ → Set β := fun u => (closure (image2 ϕ (u ∩ v) s))ᶜ
hj₁ : ∀ u ∈ f, IsOpen (j u)
hj₂ : k \ n ⊆ ⋃ u ∈ f, j u
g : Set (Set τ)
hg₁ : ∀ u ∈ g, u ∈ f
hg₂ : Set.Finite g
hg₃ : k \ n ⊆ ⋃ i ∈ g, j i
w : Set τ := (⋂ u ∈ g, u) ∩ v
hw₂ : w ∈ f
u : Set τ
hu : u ∈ g
⊢ s ⊆ s

Next tactic:
refine' iInter_subset_of_subset u (iInter_subset_of_subset hu _)