-- Mathlib/AlgebraicGeometry/Morphisms/Affine.lean
lemma isAffineOpen_of_isAffineOpen_basicOpen_aux (s : Set Γ(X, ⊤))
    (hs : Ideal.span s = ⊤) (hs₂ : ∀ i ∈ s, IsAffineOpen (X.basicOpen i)) :
    QuasiSeparatedSpace X

Proof state:
case intro.intro
X : Scheme
s : Set ↑Γ(X, ⊤)
hs : Ideal.span s = ⊤
hs₂ : ∀ i ∈ s, IsAffineOpen (X.basicOpen i)
U V : ↑X.affineOpens
s' : Finset ↑Γ(X, ⊤)
hs' : ↑s' ⊆ s
e : Ideal.span ↑s' = ⊤
⊢ IsCompact (↑↑U ∩ ↑↑V)

Tactic:
rw [← Set.inter_univ (_ ∩ _), ← Opens.coe_top, ← iSup_basicOpen_of_span_eq_top _ _ e,
  ← iSup_subtype'', Opens.coe_iSup, Set.inter_iUnion]

Result:
case intro.intro
X : Scheme
s : Set ↑Γ(X, ⊤)
hs : Ideal.span s = ⊤
hs₂ : ∀ i ∈ s, IsAffineOpen (X.basicOpen i)
U V : ↑X.affineOpens
s' : Finset ↑Γ(X, ⊤)
hs' : ↑s' ⊆ s
e : Ideal.span ↑s' = ⊤
⊢ IsCompact (⋃ i, ↑↑U ∩ ↑↑V ∩ ↑(X.basicOpen ↑i))

Proof state:
X : Scheme
s : Set ↑Γ(X, ⊤)
hs : Ideal.span s = ⊤
hs₂ : ∀ i ∈ s, IsAffineOpen (X.basicOpen i)
⊢ ∀ (U V : ↑X.affineOpens), IsCompact (↑↑U ∩ ↑↑V)

Tactic:
intros U V

Result:
X : Scheme
s : Set ↑Γ(X, ⊤)
hs : Ideal.span s = ⊤
hs₂ : ∀ i ∈ s, IsAffineOpen (X.basicOpen i)
U V : ↑X.affineOpens
⊢ IsCompact (↑↑U ∩ ↑↑V)

Proof state:
X : Scheme
s : Set ↑Γ(X, ⊤)
hs : Ideal.span s = ⊤
hs₂ : ∀ i ∈ s, IsAffineOpen (X.basicOpen i)
U V : ↑X.affineOpens
⊢ IsCompact (↑↑U ∩ ↑↑V)

Tactic:
obtain ⟨s', hs', e⟩ := (Ideal.span_eq_top_iff_finite _).mp hs

Result:
case intro.intro
X : Scheme
s : Set ↑Γ(X, ⊤)
hs : Ideal.span s = ⊤
hs₂ : ∀ i ∈ s, IsAffineOpen (X.basicOpen i)
U V : ↑X.affineOpens
s' : Finset ↑Γ(X, ⊤)
hs' : ↑s' ⊆ s
e : Ideal.span ↑s' = ⊤
⊢ IsCompact (↑↑U ∩ ↑↑V)

Proof state:
case intro.intro
X : Scheme
s : Set ↑Γ(X, ⊤)
hs : Ideal.span s = ⊤
hs₂ : ∀ i ∈ s, IsAffineOpen (X.basicOpen i)
U V : ↑X.affineOpens
s' : Finset ↑Γ(X, ⊤)
hs' : ↑s' ⊆ s
e : Ideal.span ↑s' = ⊤
⊢ IsCompact (⋃ i, ↑↑U ∩ ↑↑V ∩ ↑(X.basicOpen ↑i))

Tactic:
apply isCompact_iUnion

Result:
case intro.intro.h
X : Scheme
s : Set ↑Γ(X, ⊤)
hs : Ideal.span s = ⊤
hs₂ : ∀ i ∈ s, IsAffineOpen (X.basicOpen i)
U V : ↑X.affineOpens
s' : Finset ↑Γ(X, ⊤)
hs' : ↑s' ⊆ s
e : Ideal.span ↑s' = ⊤
⊢ ∀ (i : ↑↑s'), IsCompact (↑↑U ∩ ↑↑V ∩ ↑(X.basicOpen ↑i))

Proof state:
case intro.intro.h
X : Scheme
s : Set ↑Γ(X, ⊤)
hs : Ideal.span s = ⊤
hs₂ : ∀ i ∈ s, IsAffineOpen (X.basicOpen i)
U V : ↑X.affineOpens
s' : Finset ↑Γ(X, ⊤)
hs' : ↑s' ⊆ s
e : Ideal.span ↑s' = ⊤
i : ↑↑s'
⊢ IsCompact (↑↑U ∩ ↑(X.basicOpen ↑i) ∩ (↑↑V ∩ ↑(X.basicOpen ↑i)))

Tactic:
refine (hs₂ i (hs' i.2)).isQuasiSeparated _ _ Set.inter_subset_right
  (U.1.2.inter (X.basicOpen _).2) ?_ Set.inter_subset_right (V.1.2.inter (X.basicOpen _).2) ?_

Result:
case intro.intro.h.refine_1
X : Scheme
s : Set ↑Γ(X, ⊤)
hs : Ideal.span s = ⊤
hs₂ : ∀ i ∈ s, IsAffineOpen (X.basicOpen i)
U V : ↑X.affineOpens
s' : Finset ↑Γ(X, ⊤)
hs' : ↑s' ⊆ s
e : Ideal.span ↑s' = ⊤
i : ↑↑s'
⊢ IsCompact (↑↑U ∩ ↑(X.basicOpen ↑i))

case intro.intro.h.refine_2
X : Scheme
s : Set ↑Γ(X, ⊤)
hs : Ideal.span s = ⊤
hs₂ : ∀ i ∈ s, IsAffineOpen (X.basicOpen i)
U V : ↑X.affineOpens
s' : Finset ↑Γ(X, ⊤)
hs' : ↑s' ⊆ s
e : Ideal.span ↑s' = ⊤
i : ↑↑s'
⊢ IsCompact (↑↑V ∩ ↑(X.basicOpen ↑i))

Proof state:
X : Scheme
s : Set ↑Γ(X, ⊤)
hs : Ideal.span s = ⊤
hs₂ : ∀ i ∈ s, IsAffineOpen (X.basicOpen i)
⊢ QuasiSeparatedSpace ↑↑X.toPresheafedSpace

Tactic:
rw [quasiSeparatedSpace_iff_affine]

Result:
X : Scheme
s : Set ↑Γ(X, ⊤)
hs : Ideal.span s = ⊤
hs₂ : ∀ i ∈ s, IsAffineOpen (X.basicOpen i)
⊢ ∀ (U V : ↑X.affineOpens), IsCompact (↑↑U ∩ ↑↑V)

Proof state:
case intro.intro.h.refine_2
X : Scheme
s : Set ↑Γ(X, ⊤)
hs : Ideal.span s = ⊤
hs₂ : ∀ i ∈ s, IsAffineOpen (X.basicOpen i)
U V : ↑X.affineOpens
s' : Finset ↑Γ(X, ⊤)
hs' : ↑s' ⊆ s
e : Ideal.span ↑s' = ⊤
i : ↑↑s'
⊢ IsCompact ↑(X.basicOpen ((ConcreteCategory.hom (X.presheaf.map (homOfLE ⋯).op)) ↑i))

Tactic:
exact (V.2.basicOpen _).isCompact

Result:
no goals

Proof state:
case intro.intro.h
X : Scheme
s : Set ↑Γ(X, ⊤)
hs : Ideal.span s = ⊤
hs₂ : ∀ i ∈ s, IsAffineOpen (X.basicOpen i)
U V : ↑X.affineOpens
s' : Finset ↑Γ(X, ⊤)
hs' : ↑s' ⊆ s
e : Ideal.span ↑s' = ⊤
i : ↑↑s'
⊢ IsCompact (↑↑U ∩ ↑↑V ∩ ↑(X.basicOpen ↑i))

Tactic:
rw [Set.inter_inter_distrib_right]

Result:
case intro.intro.h
X : Scheme
s : Set ↑Γ(X, ⊤)
hs : Ideal.span s = ⊤
hs₂ : ∀ i ∈ s, IsAffineOpen (X.basicOpen i)
U V : ↑X.affineOpens
s' : Finset ↑Γ(X, ⊤)
hs' : ↑s' ⊆ s
e : Ideal.span ↑s' = ⊤
i : ↑↑s'
⊢ IsCompact (↑↑U ∩ ↑(X.basicOpen ↑i) ∩ (↑↑V ∩ ↑(X.basicOpen ↑i)))

Proof state:
case intro.intro.h.refine_1
X : Scheme
s : Set ↑Γ(X, ⊤)
hs : Ideal.span s = ⊤
hs₂ : ∀ i ∈ s, IsAffineOpen (X.basicOpen i)
U V : ↑X.affineOpens
s' : Finset ↑Γ(X, ⊤)
hs' : ↑s' ⊆ s
e : Ideal.span ↑s' = ⊤
i : ↑↑s'
⊢ IsCompact (↑↑U ∩ ↑(X.basicOpen ↑i))

Tactic:
rw [← Opens.coe_inf, ← X.basicOpen_res _ (homOfLE le_top).op]

Result:
case intro.intro.h.refine_1
X : Scheme
s : Set ↑Γ(X, ⊤)
hs : Ideal.span s = ⊤
hs₂ : ∀ i ∈ s, IsAffineOpen (X.basicOpen i)
U V : ↑X.affineOpens
s' : Finset ↑Γ(X, ⊤)
hs' : ↑s' ⊆ s
e : Ideal.span ↑s' = ⊤
i : ↑↑s'
⊢ IsCompact ↑(X.basicOpen ((ConcreteCategory.hom (X.presheaf.map (homOfLE ⋯).op)) ↑i))

Proof state:
case intro.intro.h
X : Scheme
s : Set ↑Γ(X, ⊤)
hs : Ideal.span s = ⊤
hs₂ : ∀ i ∈ s, IsAffineOpen (X.basicOpen i)
U V : ↑X.affineOpens
s' : Finset ↑Γ(X, ⊤)
hs' : ↑s' ⊆ s
e : Ideal.span ↑s' = ⊤
⊢ ∀ (i : ↑↑s'), IsCompact (↑↑U ∩ ↑↑V ∩ ↑(X.basicOpen ↑i))

Tactic:
intro i

Result:
case intro.intro.h
X : Scheme
s : Set ↑Γ(X, ⊤)
hs : Ideal.span s = ⊤
hs₂ : ∀ i ∈ s, IsAffineOpen (X.basicOpen i)
U V : ↑X.affineOpens
s' : Finset ↑Γ(X, ⊤)
hs' : ↑s' ⊆ s
e : Ideal.span ↑s' = ⊤
i : ↑↑s'
⊢ IsCompact (↑↑U ∩ ↑↑V ∩ ↑(X.basicOpen ↑i))

Proof state:
case intro.intro.h.refine_2
X : Scheme
s : Set ↑Γ(X, ⊤)
hs : Ideal.span s = ⊤
hs₂ : ∀ i ∈ s, IsAffineOpen (X.basicOpen i)
U V : ↑X.affineOpens
s' : Finset ↑Γ(X, ⊤)
hs' : ↑s' ⊆ s
e : Ideal.span ↑s' = ⊤
i : ↑↑s'
⊢ IsCompact (↑↑V ∩ ↑(X.basicOpen ↑i))

Tactic:
rw [← Opens.coe_inf, ← X.basicOpen_res _ (homOfLE le_top).op]

Result:
case intro.intro.h.refine_2
X : Scheme
s : Set ↑Γ(X, ⊤)
hs : Ideal.span s = ⊤
hs₂ : ∀ i ∈ s, IsAffineOpen (X.basicOpen i)
U V : ↑X.affineOpens
s' : Finset ↑Γ(X, ⊤)
hs' : ↑s' ⊆ s
e : Ideal.span ↑s' = ⊤
i : ↑↑s'
⊢ IsCompact ↑(X.basicOpen ((ConcreteCategory.hom (X.presheaf.map (homOfLE ⋯).op)) ↑i))

Proof state:
case intro.intro.h.refine_1
X : Scheme
s : Set ↑Γ(X, ⊤)
hs : Ideal.span s = ⊤
hs₂ : ∀ i ∈ s, IsAffineOpen (X.basicOpen i)
U V : ↑X.affineOpens
s' : Finset ↑Γ(X, ⊤)
hs' : ↑s' ⊆ s
e : Ideal.span ↑s' = ⊤
i : ↑↑s'
⊢ IsCompact ↑(X.basicOpen ((ConcreteCategory.hom (X.presheaf.map (homOfLE ⋯).op)) ↑i))

Tactic:
exact (U.2.basicOpen _).isCompact

Result:
no goals