l3lab/ntp-mathlib huggingface dataset:
theorem IsClosed.exists_minimal_nonempty_closed_subset [CompactSpace X] {S : Set X}
    (hS : IsClosed S) (hne : S.Nonempty) :
    ∃ V : Set X, V ⊆ S ∧ V.Nonempty ∧ IsClosed V ∧
      ∀ V' : Set X, V' ⊆ V → V'.Nonempty → IsClosed V' → V' = V := by
  let opens := { U : Set X | Sᶜ ⊆ U ∧ IsOpen U ∧ Uᶜ.Nonempty }
  obtain ⟨U, ⟨Uc, Uo, Ucne⟩, h⟩ :=
    zorn_subset opens fun c hc hz => by
      by_cases hcne : c.Nonempty
      · obtain ⟨U₀, hU₀⟩ := hcne
        haveI : Nonempty { U // U ∈ c } := ⟨⟨U₀, hU₀⟩⟩
        obtain ⟨U₀compl, -, -⟩ := hc hU₀
        use ⋃₀ c
        refine' ⟨⟨_, _, _⟩, fun U hU _ hx => ⟨U, hU, hx⟩⟩
        · exact fun _ hx => ⟨U₀, hU₀, U₀compl hx⟩
        · exact isOpen_sUnion fun _ h => (hc h).2.1
        · convert_to (⋂ U : { U // U ∈ c }, U.1ᶜ).Nonempty
          · ext
            simp only [not_exists, exists_prop, not_and, Set.mem_iInter, Subtype.forall,
              mem_setOf_eq, mem_compl_iff, mem_sUnion]
          apply IsCompact.nonempty_iInter_of_directed_nonempty_compact_closed
          · rintro ⟨U, hU⟩ ⟨U', hU'⟩
            obtain ⟨V, hVc, hVU, hVU'⟩ := hz.directedOn U hU U' hU'
            exact ⟨⟨V, hVc⟩, Set.compl_subset_compl.mpr hVU, Set.compl_subset_compl.mpr hVU'⟩
          · exact fun U => (hc U.2).2.2
          · exact fun U => (hc U.2).2.1.isClosed_compl.isCompact
          · exact fun U => (hc U.2).2.1.isClosed_compl
      · use Sᶜ
        refine' ⟨⟨Set.Subset.refl _, isOpen_compl_iff.mpr hS, _⟩, fun U Uc => (hcne ⟨U, Uc⟩).elim⟩
        

Proof state:
case h
X : Type u
Y : Type v
ι : Type u_1
inst✝² : TopologicalSpace X
inst✝¹ : TopologicalSpace Y
s t : Set X
inst✝ : CompactSpace X
S : Set X
hS : IsClosed S
hne : Set.Nonempty S
opens : Set (Set X) := {U | Sᶜ ⊆ U ∧ IsOpen U ∧ Set.Nonempty Uᶜ}
c : Set (Set X)
hc : c ⊆ opens
hz : IsChain (fun x x_1 => x ⊆ x_1) c
hcne : ¬Set.Nonempty c
⊢ Set.Nonempty Sᶜᶜ

Next tactic:
rw [compl_compl]
theorem IsClosed.exists_minimal_nonempty_closed_subset [CompactSpace X] {S : Set X}
    (hS : IsClosed S) (hne : S.Nonempty) :
    ∃ V : Set X, V ⊆ S ∧ V.Nonempty ∧ IsClosed V ∧
      ∀ V' : Set X, V' ⊆ V → V'.Nonempty → IsClosed V' → V' = V := by
  let opens := { U : Set X | Sᶜ ⊆ U ∧ IsOpen U ∧ Uᶜ.Nonempty }
  obtain ⟨U, ⟨Uc, Uo, Ucne⟩, h⟩ :=
    zorn_subset opens fun c hc hz => by
      by_cases hcne : c.Nonempty
      · obtain ⟨U₀, hU₀⟩ := hcne
        haveI : Nonempty { U // U ∈ c } := ⟨⟨U₀, hU₀⟩⟩
        obtain ⟨U₀compl, -, -⟩ := hc hU₀
        use ⋃₀ c
        refine' ⟨⟨_, _, _⟩, fun U hU _ hx => ⟨U, hU, hx⟩⟩
        · exact fun _ hx => ⟨U₀, hU₀, U₀compl hx⟩
        · exact isOpen_sUnion fun _ h => (hc h).2.1
        · convert_to (⋂ U : { U // U ∈ c }, U.1ᶜ).Nonempty
          · ext
            simp only [not_exists, exists_prop, not_and, Set.mem_iInter, Subtype.forall,
              mem_setOf_eq, mem_compl_iff, mem_sUnion]
          apply IsCompact.nonempty_iInter_of_directed_nonempty_compact_closed
          · rintro ⟨U, hU⟩ ⟨U', hU'⟩
            obtain ⟨V, hVc, hVU, hVU'⟩ := hz.directedOn U hU U' hU'
            exact ⟨⟨V, hVc⟩, Set.compl_subset_compl.mpr hVU, Set.compl_subset_compl.mpr hVU'⟩
          · exact fun U => (hc U.2).2.2
          · exact fun U => (hc U.2).2.1.isClosed_compl.isCompact
          · exact fun U => (hc U.2).2.1.isClosed_compl
      · use Sᶜ
        refine' ⟨⟨Set.Subset.refl _, isOpen_compl_iff.mpr hS, _⟩, fun U Uc => (hcne ⟨U, Uc⟩).elim⟩
        rw [compl_compl]
        

Proof state:
case h
X : Type u
Y : Type v
ι : Type u_1
inst✝² : TopologicalSpace X
inst✝¹ : TopologicalSpace Y
s t : Set X
inst✝ : CompactSpace X
S : Set X
hS : IsClosed S
hne : Set.Nonempty S
opens : Set (Set X) := {U | Sᶜ ⊆ U ∧ IsOpen U ∧ Set.Nonempty Uᶜ}
c : Set (Set X)
hc : c ⊆ opens
hz : IsChain (fun x x_1 => x ⊆ x_1) c
hcne : ¬Set.Nonempty c
⊢ Set.Nonempty S

Next tactic:
exact hne
theorem IsClosed.exists_minimal_nonempty_closed_subset [CompactSpace X] {S : Set X}
    (hS : IsClosed S) (hne : S.Nonempty) :
    ∃ V : Set X, V ⊆ S ∧ V.Nonempty ∧ IsClosed V ∧
      ∀ V' : Set X, V' ⊆ V → V'.Nonempty → IsClosed V' → V' = V := by
  let opens := { U : Set X | Sᶜ ⊆ U ∧ IsOpen U ∧ Uᶜ.Nonempty }
  obtain ⟨U, ⟨Uc, Uo, Ucne⟩, h⟩ :=
    zorn_subset opens fun c hc hz => by
      by_cases hcne : c.Nonempty
      · obtain ⟨U₀, hU₀⟩ := hcne
        haveI : Nonempty { U // U ∈ c } := ⟨⟨U₀, hU₀⟩⟩
        obtain ⟨U₀compl, -, -⟩ := hc hU₀
        use ⋃₀ c
        refine' ⟨⟨_, _, _⟩, fun U hU _ hx => ⟨U, hU, hx⟩⟩
        · exact fun _ hx => ⟨U₀, hU₀, U₀compl hx⟩
        · exact isOpen_sUnion fun _ h => (hc h).2.1
        · convert_to (⋂ U : { U // U ∈ c }, U.1ᶜ).Nonempty
          · ext
            simp only [not_exists, exists_prop, not_and, Set.mem_iInter, Subtype.forall,
              mem_setOf_eq, mem_compl_iff, mem_sUnion]
          apply IsCompact.nonempty_iInter_of_directed_nonempty_compact_closed
          · rintro ⟨U, hU⟩ ⟨U', hU'⟩
            obtain ⟨V, hVc, hVU, hVU'⟩ := hz.directedOn U hU U' hU'
            exact ⟨⟨V, hVc⟩, Set.compl_subset_compl.mpr hVU, Set.compl_subset_compl.mpr hVU'⟩
          · exact fun U => (hc U.2).2.2
          · exact fun U => (hc U.2).2.1.isClosed_compl.isCompact
          · exact fun U => (hc U.2).2.1.isClosed_compl
      · use Sᶜ
        refine' ⟨⟨Set.Subset.refl _, isOpen_compl_iff.mpr hS, _⟩, fun U Uc => (hcne ⟨U, Uc⟩).elim⟩
        rw [compl_compl]
        exact hne
  

Proof state:
case intro.intro.intro.intro
X : Type u
Y : Type v
ι : Type u_1
inst✝² : TopologicalSpace X
inst✝¹ : TopologicalSpace Y
s t : Set X
inst✝ : CompactSpace X
S : Set X
hS : IsClosed S
hne : Set.Nonempty S
opens : Set (Set X) := {U | Sᶜ ⊆ U ∧ IsOpen U ∧ Set.Nonempty Uᶜ}
U : Set X
h : ∀ a ∈ opens, U ⊆ a → a = U
Uc : Sᶜ ⊆ U
Uo : IsOpen U
Ucne : Set.Nonempty Uᶜ
⊢ ∃ V ⊆ S, Set.Nonempty V ∧ IsClosed V ∧ ∀ V' ⊆ V, Set.Nonempty V' → IsClosed V' → V' = V

Next tactic:
refine' ⟨Uᶜ, Set.compl_subset_comm.mp Uc, Ucne, Uo.isClosed_compl, _⟩
theorem IsClosed.exists_minimal_nonempty_closed_subset [CompactSpace X] {S : Set X}
    (hS : IsClosed S) (hne : S.Nonempty) :
    ∃ V : Set X, V ⊆ S ∧ V.Nonempty ∧ IsClosed V ∧
      ∀ V' : Set X, V' ⊆ V → V'.Nonempty → IsClosed V' → V' = V := by
  let opens := { U : Set X | Sᶜ ⊆ U ∧ IsOpen U ∧ Uᶜ.Nonempty }
  obtain ⟨U, ⟨Uc, Uo, Ucne⟩, h⟩ :=
    zorn_subset opens fun c hc hz => by
      by_cases hcne : c.Nonempty
      · obtain ⟨U₀, hU₀⟩ := hcne
        haveI : Nonempty { U // U ∈ c } := ⟨⟨U₀, hU₀⟩⟩
        obtain ⟨U₀compl, -, -⟩ := hc hU₀
        use ⋃₀ c
        refine' ⟨⟨_, _, _⟩, fun U hU _ hx => ⟨U, hU, hx⟩⟩
        · exact fun _ hx => ⟨U₀, hU₀, U₀compl hx⟩
        · exact isOpen_sUnion fun _ h => (hc h).2.1
        · convert_to (⋂ U : { U // U ∈ c }, U.1ᶜ).Nonempty
          · ext
            simp only [not_exists, exists_prop, not_and, Set.mem_iInter, Subtype.forall,
              mem_setOf_eq, mem_compl_iff, mem_sUnion]
          apply IsCompact.nonempty_iInter_of_directed_nonempty_compact_closed
          · rintro ⟨U, hU⟩ ⟨U', hU'⟩
            obtain ⟨V, hVc, hVU, hVU'⟩ := hz.directedOn U hU U' hU'
            exact ⟨⟨V, hVc⟩, Set.compl_subset_compl.mpr hVU, Set.compl_subset_compl.mpr hVU'⟩
          · exact fun U => (hc U.2).2.2
          · exact fun U => (hc U.2).2.1.isClosed_compl.isCompact
          · exact fun U => (hc U.2).2.1.isClosed_compl
      · use Sᶜ
        refine' ⟨⟨Set.Subset.refl _, isOpen_compl_iff.mpr hS, _⟩, fun U Uc => (hcne ⟨U, Uc⟩).elim⟩
        rw [compl_compl]
        exact hne
  refine' ⟨Uᶜ, Set.compl_subset_comm.mp Uc, Ucne, Uo.isClosed_compl, _⟩
  

Proof state:
case intro.intro.intro.intro
X : Type u
Y : Type v
ι : Type u_1
inst✝² : TopologicalSpace X
inst✝¹ : TopologicalSpace Y
s t : Set X
inst✝ : CompactSpace X
S : Set X
hS : IsClosed S
hne : Set.Nonempty S
opens : Set (Set X) := {U | Sᶜ ⊆ U ∧ IsOpen U ∧ Set.Nonempty Uᶜ}
U : Set X
h : ∀ a ∈ opens, U ⊆ a → a = U
Uc : Sᶜ ⊆ U
Uo : IsOpen U
Ucne : Set.Nonempty Uᶜ
⊢ ∀ V' ⊆ Uᶜ, Set.Nonempty V' → IsClosed V' → V' = Uᶜ

Next tactic:
intro V' V'sub V'ne V'cls
theorem IsClosed.exists_minimal_nonempty_closed_subset [CompactSpace X] {S : Set X}
    (hS : IsClosed S) (hne : S.Nonempty) :
    ∃ V : Set X, V ⊆ S ∧ V.Nonempty ∧ IsClosed V ∧
      ∀ V' : Set X, V' ⊆ V → V'.Nonempty → IsClosed V' → V' = V := by
  let opens := { U : Set X | Sᶜ ⊆ U ∧ IsOpen U ∧ Uᶜ.Nonempty }
  obtain ⟨U, ⟨Uc, Uo, Ucne⟩, h⟩ :=
    zorn_subset opens fun c hc hz => by
      by_cases hcne : c.Nonempty
      · obtain ⟨U₀, hU₀⟩ := hcne
        haveI : Nonempty { U // U ∈ c } := ⟨⟨U₀, hU₀⟩⟩
        obtain ⟨U₀compl, -, -⟩ := hc hU₀
        use ⋃₀ c
        refine' ⟨⟨_, _, _⟩, fun U hU _ hx => ⟨U, hU, hx⟩⟩
        · exact fun _ hx => ⟨U₀, hU₀, U₀compl hx⟩
        · exact isOpen_sUnion fun _ h => (hc h).2.1
        · convert_to (⋂ U : { U // U ∈ c }, U.1ᶜ).Nonempty
          · ext
            simp only [not_exists, exists_prop, not_and, Set.mem_iInter, Subtype.forall,
              mem_setOf_eq, mem_compl_iff, mem_sUnion]
          apply IsCompact.nonempty_iInter_of_directed_nonempty_compact_closed
          · rintro ⟨U, hU⟩ ⟨U', hU'⟩
            obtain ⟨V, hVc, hVU, hVU'⟩ := hz.directedOn U hU U' hU'
            exact ⟨⟨V, hVc⟩, Set.compl_subset_compl.mpr hVU, Set.compl_subset_compl.mpr hVU'⟩
          · exact fun U => (hc U.2).2.2
          · exact fun U => (hc U.2).2.1.isClosed_compl.isCompact
          · exact fun U => (hc U.2).2.1.isClosed_compl
      · use Sᶜ
        refine' ⟨⟨Set.Subset.refl _, isOpen_compl_iff.mpr hS, _⟩, fun U Uc => (hcne ⟨U, Uc⟩).elim⟩
        rw [compl_compl]
        exact hne
  refine' ⟨Uᶜ, Set.compl_subset_comm.mp Uc, Ucne, Uo.isClosed_compl, _⟩
  intro V' V'sub V'ne V'cls
  

Proof state:
case intro.intro.intro.intro
X : Type u
Y : Type v
ι : Type u_1
inst✝² : TopologicalSpace X
inst✝¹ : TopologicalSpace Y
s t : Set X
inst✝ : CompactSpace X
S : Set X
hS : IsClosed S
hne : Set.Nonempty S
opens : Set (Set X) := {U | Sᶜ ⊆ U ∧ IsOpen U ∧ Set.Nonempty Uᶜ}
U : Set X
h : ∀ a ∈ opens, U ⊆ a → a = U
Uc : Sᶜ ⊆ U
Uo : IsOpen U
Ucne : Set.Nonempty Uᶜ
V' : Set X
V'sub : V' ⊆ Uᶜ
V'ne : Set.Nonempty V'
V'cls : IsClosed V'
⊢ V' = Uᶜ

Next tactic:
have : V'ᶜ = U := by
    refine' h V'ᶜ ⟨_, isOpen_compl_iff.mpr V'cls, _⟩ (Set.subset_compl_comm.mp V'sub)
    exact Set.Subset.trans Uc (Set.subset_compl_comm.mp V'sub)
    simp only [compl_compl, V'ne]
theorem IsClosed.exists_minimal_nonempty_closed_subset [CompactSpace X] {S : Set X}
    (hS : IsClosed S) (hne : S.Nonempty) :
    ∃ V : Set X, V ⊆ S ∧ V.Nonempty ∧ IsClosed V ∧
      ∀ V' : Set X, V' ⊆ V → V'.Nonempty → IsClosed V' → V' = V := by
  let opens := { U : Set X | Sᶜ ⊆ U ∧ IsOpen U ∧ Uᶜ.Nonempty }
  obtain ⟨U, ⟨Uc, Uo, Ucne⟩, h⟩ :=
    zorn_subset opens fun c hc hz => by
      by_cases hcne : c.Nonempty
      · obtain ⟨U₀, hU₀⟩ := hcne
        haveI : Nonempty { U // U ∈ c } := ⟨⟨U₀, hU₀⟩⟩
        obtain ⟨U₀compl, -, -⟩ := hc hU₀
        use ⋃₀ c
        refine' ⟨⟨_, _, _⟩, fun U hU _ hx => ⟨U, hU, hx⟩⟩
        · exact fun _ hx => ⟨U₀, hU₀, U₀compl hx⟩
        · exact isOpen_sUnion fun _ h => (hc h).2.1
        · convert_to (⋂ U : { U // U ∈ c }, U.1ᶜ).Nonempty
          · ext
            simp only [not_exists, exists_prop, not_and, Set.mem_iInter, Subtype.forall,
              mem_setOf_eq, mem_compl_iff, mem_sUnion]
          apply IsCompact.nonempty_iInter_of_directed_nonempty_compact_closed
          · rintro ⟨U, hU⟩ ⟨U', hU'⟩
            obtain ⟨V, hVc, hVU, hVU'⟩ := hz.directedOn U hU U' hU'
            exact ⟨⟨V, hVc⟩, Set.compl_subset_compl.mpr hVU, Set.compl_subset_compl.mpr hVU'⟩
          · exact fun U => (hc U.2).2.2
          · exact fun U => (hc U.2).2.1.isClosed_compl.isCompact
          · exact fun U => (hc U.2).2.1.isClosed_compl
      · use Sᶜ
        refine' ⟨⟨Set.Subset.refl _, isOpen_compl_iff.mpr hS, _⟩, fun U Uc => (hcne ⟨U, Uc⟩).elim⟩
        rw [compl_compl]
        exact hne
  refine' ⟨Uᶜ, Set.compl_subset_comm.mp Uc, Ucne, Uo.isClosed_compl, _⟩
  intro V' V'sub V'ne V'cls
  have : V'ᶜ = U := by
    

Proof state:
X : Type u
Y : Type v
ι : Type u_1
inst✝² : TopologicalSpace X
inst✝¹ : TopologicalSpace Y
s t : Set X
inst✝ : CompactSpace X
S : Set X
hS : IsClosed S
hne : Set.Nonempty S
opens : Set (Set X) := {U | Sᶜ ⊆ U ∧ IsOpen U ∧ Set.Nonempty Uᶜ}
U : Set X
h : ∀ a ∈ opens, U ⊆ a → a = U
Uc : Sᶜ ⊆ U
Uo : IsOpen U
Ucne : Set.Nonempty Uᶜ
V' : Set X
V'sub : V' ⊆ Uᶜ
V'ne : Set.Nonempty V'
V'cls : IsClosed V'
⊢ V'ᶜ = U

Next tactic:
refine' h V'ᶜ ⟨_, isOpen_compl_iff.mpr V'cls, _⟩ (Set.subset_compl_comm.mp V'sub)
theorem IsClosed.exists_minimal_nonempty_closed_subset [CompactSpace X] {S : Set X}
    (hS : IsClosed S) (hne : S.Nonempty) :
    ∃ V : Set X, V ⊆ S ∧ V.Nonempty ∧ IsClosed V ∧
      ∀ V' : Set X, V' ⊆ V → V'.Nonempty → IsClosed V' → V' = V := by
  let opens := { U : Set X | Sᶜ ⊆ U ∧ IsOpen U ∧ Uᶜ.Nonempty }
  obtain ⟨U, ⟨Uc, Uo, Ucne⟩, h⟩ :=
    zorn_subset opens fun c hc hz => by
      by_cases hcne : c.Nonempty
      · obtain ⟨U₀, hU₀⟩ := hcne
        haveI : Nonempty { U // U ∈ c } := ⟨⟨U₀, hU₀⟩⟩
        obtain ⟨U₀compl, -, -⟩ := hc hU₀
        use ⋃₀ c
        refine' ⟨⟨_, _, _⟩, fun U hU _ hx => ⟨U, hU, hx⟩⟩
        · exact fun _ hx => ⟨U₀, hU₀, U₀compl hx⟩
        · exact isOpen_sUnion fun _ h => (hc h).2.1
        · convert_to (⋂ U : { U // U ∈ c }, U.1ᶜ).Nonempty
          · ext
            simp only [not_exists, exists_prop, not_and, Set.mem_iInter, Subtype.forall,
              mem_setOf_eq, mem_compl_iff, mem_sUnion]
          apply IsCompact.nonempty_iInter_of_directed_nonempty_compact_closed
          · rintro ⟨U, hU⟩ ⟨U', hU'⟩
            obtain ⟨V, hVc, hVU, hVU'⟩ := hz.directedOn U hU U' hU'
            exact ⟨⟨V, hVc⟩, Set.compl_subset_compl.mpr hVU, Set.compl_subset_compl.mpr hVU'⟩
          · exact fun U => (hc U.2).2.2
          · exact fun U => (hc U.2).2.1.isClosed_compl.isCompact
          · exact fun U => (hc U.2).2.1.isClosed_compl
      · use Sᶜ
        refine' ⟨⟨Set.Subset.refl _, isOpen_compl_iff.mpr hS, _⟩, fun U Uc => (hcne ⟨U, Uc⟩).elim⟩
        rw [compl_compl]
        exact hne
  refine' ⟨Uᶜ, Set.compl_subset_comm.mp Uc, Ucne, Uo.isClosed_compl, _⟩
  intro V' V'sub V'ne V'cls
  have : V'ᶜ = U := by
    refine' h V'ᶜ ⟨_, isOpen_compl_iff.mpr V'cls, _⟩ (Set.subset_compl_comm.mp V'sub)
    

Proof state:
case refine'_1
X : Type u
Y : Type v
ι : Type u_1
inst✝² : TopologicalSpace X
inst✝¹ : TopologicalSpace Y
s t : Set X
inst✝ : CompactSpace X
S : Set X
hS : IsClosed S
hne : Set.Nonempty S
opens : Set (Set X) := {U | Sᶜ ⊆ U ∧ IsOpen U ∧ Set.Nonempty Uᶜ}
U : Set X
h : ∀ a ∈ opens, U ⊆ a → a = U
Uc : Sᶜ ⊆ U
Uo : IsOpen U
Ucne : Set.Nonempty Uᶜ
V' : Set X
V'sub : V' ⊆ Uᶜ
V'ne : Set.Nonempty V'
V'cls : IsClosed V'
⊢ Sᶜ ⊆ V'ᶜ
case refine'_2
X : Type u
Y : Type v
ι : Type u_1
inst✝² : TopologicalSpace X
inst✝¹ : TopologicalSpace Y
s t : Set X
inst✝ : CompactSpace X
S : Set X
hS : IsClosed S
hne : Set.Nonempty S
opens : Set (Set X) := {U | Sᶜ ⊆ U ∧ IsOpen U ∧ Set.Nonempty Uᶜ}
U : Set X
h : ∀ a ∈ opens, U ⊆ a → a = U
Uc : Sᶜ ⊆ U
Uo : IsOpen U
Ucne : Set.Nonempty Uᶜ
V' : Set X
V'sub : V' ⊆ Uᶜ
V'ne : Set.Nonempty V'
V'cls : IsClosed V'
⊢ Set.Nonempty V'ᶜᶜ

Next tactic:
exact Set.Subset.trans Uc (Set.subset_compl_comm.mp V'sub)
theorem IsClosed.exists_minimal_nonempty_closed_subset [CompactSpace X] {S : Set X}
    (hS : IsClosed S) (hne : S.Nonempty) :
    ∃ V : Set X, V ⊆ S ∧ V.Nonempty ∧ IsClosed V ∧
      ∀ V' : Set X, V' ⊆ V → V'.Nonempty → IsClosed V' → V' = V := by
  let opens := { U : Set X | Sᶜ ⊆ U ∧ IsOpen U ∧ Uᶜ.Nonempty }
  obtain ⟨U, ⟨Uc, Uo, Ucne⟩, h⟩ :=
    zorn_subset opens fun c hc hz => by
      by_cases hcne : c.Nonempty
      · obtain ⟨U₀, hU₀⟩ := hcne
        haveI : Nonempty { U // U ∈ c } := ⟨⟨U₀, hU₀⟩⟩
        obtain ⟨U₀compl, -, -⟩ := hc hU₀
        use ⋃₀ c
        refine' ⟨⟨_, _, _⟩, fun U hU _ hx => ⟨U, hU, hx⟩⟩
        · exact fun _ hx => ⟨U₀, hU₀, U₀compl hx⟩
        · exact isOpen_sUnion fun _ h => (hc h).2.1
        · convert_to (⋂ U : { U // U ∈ c }, U.1ᶜ).Nonempty
          · ext
            simp only [not_exists, exists_prop, not_and, Set.mem_iInter, Subtype.forall,
              mem_setOf_eq, mem_compl_iff, mem_sUnion]
          apply IsCompact.nonempty_iInter_of_directed_nonempty_compact_closed
          · rintro ⟨U, hU⟩ ⟨U', hU'⟩
            obtain ⟨V, hVc, hVU, hVU'⟩ := hz.directedOn U hU U' hU'
            exact ⟨⟨V, hVc⟩, Set.compl_subset_compl.mpr hVU, Set.compl_subset_compl.mpr hVU'⟩
          · exact fun U => (hc U.2).2.2
          · exact fun U => (hc U.2).2.1.isClosed_compl.isCompact
          · exact fun U => (hc U.2).2.1.isClosed_compl
      · use Sᶜ
        refine' ⟨⟨Set.Subset.refl _, isOpen_compl_iff.mpr hS, _⟩, fun U Uc => (hcne ⟨U, Uc⟩).elim⟩
        rw [compl_compl]
        exact hne
  refine' ⟨Uᶜ, Set.compl_subset_comm.mp Uc, Ucne, Uo.isClosed_compl, _⟩
  intro V' V'sub V'ne V'cls
  have : V'ᶜ = U := by
    refine' h V'ᶜ ⟨_, isOpen_compl_iff.mpr V'cls, _⟩ (Set.subset_compl_comm.mp V'sub)
    exact Set.Subset.trans Uc (Set.subset_compl_comm.mp V'sub)
    

Proof state:
case refine'_2
X : Type u
Y : Type v
ι : Type u_1
inst✝² : TopologicalSpace X
inst✝¹ : TopologicalSpace Y
s t : Set X
inst✝ : CompactSpace X
S : Set X
hS : IsClosed S
hne : Set.Nonempty S
opens : Set (Set X) := {U | Sᶜ ⊆ U ∧ IsOpen U ∧ Set.Nonempty Uᶜ}
U : Set X
h : ∀ a ∈ opens, U ⊆ a → a = U
Uc : Sᶜ ⊆ U
Uo : IsOpen U
Ucne : Set.Nonempty Uᶜ
V' : Set X
V'sub : V' ⊆ Uᶜ
V'ne : Set.Nonempty V'
V'cls : IsClosed V'
⊢ Set.Nonempty V'ᶜᶜ

Next tactic:
simp only [compl_compl, V'ne]
theorem IsClosed.exists_minimal_nonempty_closed_subset [CompactSpace X] {S : Set X}
    (hS : IsClosed S) (hne : S.Nonempty) :
    ∃ V : Set X, V ⊆ S ∧ V.Nonempty ∧ IsClosed V ∧
      ∀ V' : Set X, V' ⊆ V → V'.Nonempty → IsClosed V' → V' = V := by
  let opens := { U : Set X | Sᶜ ⊆ U ∧ IsOpen U ∧ Uᶜ.Nonempty }
  obtain ⟨U, ⟨Uc, Uo, Ucne⟩, h⟩ :=
    zorn_subset opens fun c hc hz => by
      by_cases hcne : c.Nonempty
      · obtain ⟨U₀, hU₀⟩ := hcne
        haveI : Nonempty { U // U ∈ c } := ⟨⟨U₀, hU₀⟩⟩
        obtain ⟨U₀compl, -, -⟩ := hc hU₀
        use ⋃₀ c
        refine' ⟨⟨_, _, _⟩, fun U hU _ hx => ⟨U, hU, hx⟩⟩
        · exact fun _ hx => ⟨U₀, hU₀, U₀compl hx⟩
        · exact isOpen_sUnion fun _ h => (hc h).2.1
        · convert_to (⋂ U : { U // U ∈ c }, U.1ᶜ).Nonempty
          · ext
            simp only [not_exists, exists_prop, not_and, Set.mem_iInter, Subtype.forall,
              mem_setOf_eq, mem_compl_iff, mem_sUnion]
          apply IsCompact.nonempty_iInter_of_directed_nonempty_compact_closed
          · rintro ⟨U, hU⟩ ⟨U', hU'⟩
            obtain ⟨V, hVc, hVU, hVU'⟩ := hz.directedOn U hU U' hU'
            exact ⟨⟨V, hVc⟩, Set.compl_subset_compl.mpr hVU, Set.compl_subset_compl.mpr hVU'⟩
          · exact fun U => (hc U.2).2.2
          · exact fun U => (hc U.2).2.1.isClosed_compl.isCompact
          · exact fun U => (hc U.2).2.1.isClosed_compl
      · use Sᶜ
        refine' ⟨⟨Set.Subset.refl _, isOpen_compl_iff.mpr hS, _⟩, fun U Uc => (hcne ⟨U, Uc⟩).elim⟩
        rw [compl_compl]
        exact hne
  refine' ⟨Uᶜ, Set.compl_subset_comm.mp Uc, Ucne, Uo.isClosed_compl, _⟩
  intro V' V'sub V'ne V'cls
  have : V'ᶜ = U := by
    refine' h V'ᶜ ⟨_, isOpen_compl_iff.mpr V'cls, _⟩ (Set.subset_compl_comm.mp V'sub)
    exact Set.Subset.trans Uc (Set.subset_compl_comm.mp V'sub)
    simp only [compl_compl, V'ne]
  

Proof state:
case intro.intro.intro.intro
X : Type u
Y : Type v
ι : Type u_1
inst✝² : TopologicalSpace X
inst✝¹ : TopologicalSpace Y
s t : Set X
inst✝ : CompactSpace X
S : Set X
hS : IsClosed S
hne : Set.Nonempty S
opens : Set (Set X) := {U | Sᶜ ⊆ U ∧ IsOpen U ∧ Set.Nonempty Uᶜ}
U : Set X
h : ∀ a ∈ opens, U ⊆ a → a = U
Uc : Sᶜ ⊆ U
Uo : IsOpen U
Ucne : Set.Nonempty Uᶜ
V' : Set X
V'sub : V' ⊆ Uᶜ
V'ne : Set.Nonempty V'
V'cls : IsClosed V'
this : V'ᶜ = U
⊢ V' = Uᶜ

Next tactic:
rw [← this, compl_compl]
theorem omegaLimit_subset_of_tendsto {m : τ → τ} {f₁ f₂ : Filter τ} (hf : Tendsto m f₁ f₂) :
    ω f₁ (fun t x ↦ ϕ (m t) x) s ⊆ ω f₂ ϕ s := by
  

Proof state:
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
m : τ → τ
f₁ f₂ : Filter τ
hf : Tendsto m f₁ f₂
⊢ ω f₁ (fun t x => ϕ (m t) x) s ⊆ ω f₂ ϕ s

Next tactic:
refine' iInter₂_mono' fun u hu ↦ ⟨m ⁻¹' u, tendsto_def.mp hf _ hu, _⟩
theorem omegaLimit_subset_of_tendsto {m : τ → τ} {f₁ f₂ : Filter τ} (hf : Tendsto m f₁ f₂) :
    ω f₁ (fun t x ↦ ϕ (m t) x) s ⊆ ω f₂ ϕ s := by
  refine' iInter₂_mono' fun u hu ↦ ⟨m ⁻¹' u, tendsto_def.mp hf _ hu, _⟩
  

Proof state:
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
m : τ → τ
f₁ f₂ : Filter τ
hf : Tendsto m f₁ f₂
u : Set τ
hu : u ∈ f₂
⊢ closure (image2 (fun t x => ϕ (m t) x) (m ⁻¹' u) s) ⊆ closure (image2 ϕ u s)

Next tactic:
rw [← image2_image_left]
theorem omegaLimit_subset_of_tendsto {m : τ → τ} {f₁ f₂ : Filter τ} (hf : Tendsto m f₁ f₂) :
    ω f₁ (fun t x ↦ ϕ (m t) x) s ⊆ ω f₂ ϕ s := by
  refine' iInter₂_mono' fun u hu ↦ ⟨m ⁻¹' u, tendsto_def.mp hf _ hu, _⟩
  rw [← image2_image_left]
  

Proof state:
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
m : τ → τ
f₁ f₂ : Filter τ
hf : Tendsto m f₁ f₂
u : Set τ
hu : u ∈ f₂
⊢ closure (image2 ϕ ((fun t => m t) '' (m ⁻¹' u)) s) ⊆ closure (image2 ϕ u s)

Next tactic:
exact closure_mono (image2_subset (image_preimage_subset _ _) Subset.rfl)
theorem mapsTo_omegaLimit' {α' β' : Type*} [TopologicalSpace β'] {f : Filter τ} {ϕ : τ → α → β}
    {ϕ' : τ → α' → β'} {ga : α → α'} {s' : Set α'} (hs : MapsTo ga s s') {gb : β → β'}
    (hg : ∀ᶠ t in f, EqOn (gb ∘ ϕ t) (ϕ' t ∘ ga) s) (hgc : Continuous gb) :
    MapsTo gb (ω f ϕ s) (ω f ϕ' s') := by
  

Proof state:
τ : Type u_1
α : Type u_2
β : Type u_3
ι : Type u_4
inst✝¹ : TopologicalSpace β
f✝ : Filter τ
ϕ✝ : τ → α → β
s s₁ s₂ : Set α
α' : Type u_5
β' : Type u_6
inst✝ : TopologicalSpace β'
f : Filter τ
ϕ : τ → α → β
ϕ' : τ → α' → β'
ga : α → α'
s' : Set α'
hs : MapsTo ga s s'
gb : β → β'
hg : ∀ᶠ (t : τ) in f, EqOn (gb ∘ ϕ t) (ϕ' t ∘ ga) s
hgc : Continuous gb
⊢ MapsTo gb (ω f ϕ s) (ω f ϕ' s')

Next tactic:
simp only [omegaLimit_def, mem_iInter, MapsTo]
theorem mapsTo_omegaLimit' {α' β' : Type*} [TopologicalSpace β'] {f : Filter τ} {ϕ : τ → α → β}
    {ϕ' : τ → α' → β'} {ga : α → α'} {s' : Set α'} (hs : MapsTo ga s s') {gb : β → β'}
    (hg : ∀ᶠ t in f, EqOn (gb ∘ ϕ t) (ϕ' t ∘ ga) s) (hgc : Continuous gb) :
    MapsTo gb (ω f ϕ s) (ω f ϕ' s') := by
  simp only [omegaLimit_def, mem_iInter, MapsTo]
  

Proof state:
τ : Type u_1
α : Type u_2
β : Type u_3
ι : Type u_4
inst✝¹ : TopologicalSpace β
f✝ : Filter τ
ϕ✝ : τ → α → β
s s₁ s₂ : Set α
α' : Type u_5
β' : Type u_6
inst✝ : TopologicalSpace β'
f : Filter τ
ϕ : τ → α → β
ϕ' : τ → α' → β'
ga : α → α'
s' : Set α'
hs : MapsTo ga s s'
gb : β → β'
hg : ∀ᶠ (t : τ) in f, EqOn (gb ∘ ϕ t) (ϕ' t ∘ ga) s
hgc : Continuous gb
⊢ ∀ ⦃x : β⦄, (∀ i ∈ f, x ∈ closure (image2 ϕ i s)) → ∀ i ∈ f, gb x ∈ closure (image2 ϕ' i s')

Next tactic:
intro y hy u hu
theorem mapsTo_omegaLimit' {α' β' : Type*} [TopologicalSpace β'] {f : Filter τ} {ϕ : τ → α → β}
    {ϕ' : τ → α' → β'} {ga : α → α'} {s' : Set α'} (hs : MapsTo ga s s') {gb : β → β'}
    (hg : ∀ᶠ t in f, EqOn (gb ∘ ϕ t) (ϕ' t ∘ ga) s) (hgc : Continuous gb) :
    MapsTo gb (ω f ϕ s) (ω f ϕ' s') := by
  simp only [omegaLimit_def, mem_iInter, MapsTo]
  intro y hy u hu
  

Proof state:
τ : Type u_1
α : Type u_2
β : Type u_3
ι : Type u_4
inst✝¹ : TopologicalSpace β
f✝ : Filter τ
ϕ✝ : τ → α → β
s s₁ s₂ : Set α
α' : Type u_5
β' : Type u_6
inst✝ : TopologicalSpace β'
f : Filter τ
ϕ : τ → α → β
ϕ' : τ → α' → β'
ga : α → α'
s' : Set α'
hs : MapsTo ga s s'
gb : β → β'
hg : ∀ᶠ (t : τ) in f, EqOn (gb ∘ ϕ t) (ϕ' t ∘ ga) s
hgc : Continuous gb
y : β
hy : ∀ i ∈ f, y ∈ closure (image2 ϕ i s)
u : Set τ
hu : u ∈ f
⊢ gb y ∈ closure (image2 ϕ' u s')

Next tactic:
refine' map_mem_closure hgc (hy _ (inter_mem hu hg)) (forall_image2_iff.2 fun t ht x hx ↦ _)