Module: Mathlib.AlgebraicGeometry.ZariskisMainTheorem

Goal state before:
pp: X S : Scheme
f : X ⟶ S
inst✝¹ : LocallyOfFiniteType f
inst✝ : IsSeparated f
x : ↥X
s : ↥S
h : f x = s
hx : Scheme.Hom.QuasiFiniteAt f x
U : TopologicalSpace.Opens ↥S
hU : U ∈ S.affineOpens
hxU : f x ∈ ↑U
V : TopologicalSpace.Opens ↥X
hV : V ∈ X.affineOpens
hxV : x ∈ ↑V
hUV : V ≤ f ⁻¹ᵁ U
this✝⁵ : (CommRingCat.Hom.hom (Scheme.Hom.appLE f U V hUV)).FiniteType
algInst✝ : Algebra ↑Γ(S, U) ↑Γ(X, V) := (CommRingCat.Hom.hom (Scheme.Hom.appLE f U V hUV)).toAlgebra
algebraizeInst✝ : Algebra.FiniteType ↑Γ(S, U) ↑Γ(X, V)
this✝⁴ : (IsAffineOpen.primeIdealOf hV ⟨x, hxV⟩).asIdeal.LiesOver (IsAffineOpen.primeIdealOf hU ⟨f x, hxU⟩).asIdeal
this✝³ : Algebra.QuasiFiniteAt (↑Γ(S, U)) (IsAffineOpen.primeIdealOf hV ⟨x, hxV⟩).asIdeal
R : Type u
w✝⁷ : CommRing R
w✝⁶ : Algebra (↑Γ(S, U)) R
w✝⁵ : Algebra.Etale (↑Γ(S, U)) R
P : Ideal R
w✝⁴ : P.IsPrime
w✝³ : P.LiesOver (IsAffineOpen.primeIdealOf hU ⟨f x, hxU⟩).asIdeal
e : R ⊗[↑Γ(S, U)] ↑Γ(X, V)
w✝² : IsIdempotentElem e
P' : Ideal (R ⊗[↑Γ(S, U)] ↑Γ(X, V))
w✝¹ : P'.IsPrime
w✝ : P'.LiesOver P
hP' : Ideal.comap Algebra.TensorProduct.includeRight.toRingHom P' = (IsAffineOpen.primeIdealOf hV ⟨x, hxV⟩).asIdeal
heP' : e ∉ P'
left✝ : Module.Finite R (Localization.Away e)
this✝² : (algebraMap R (Localization.Away e)).Finite
φ : Γ(S, U) ⟶ CommRingCat.of R := CommRingCat.ofHom (algebraMap (↑Γ(S, U)) R)
hφ : (CommRingCat.Hom.hom φ).Etale
this✝¹ : Etale (Spec.map φ)
e₁ : Spec (CommRingCat.of (R ⊗[↑Γ(S, U)] ↑Γ(X, V))) ≅ pullback (Spec.map (Scheme.Hom.appLE f U V hUV)) (Spec.map φ) :=
  (pullbackSpecIso (↑Γ(S, U)) R ↑Γ(X, V)).symm ≪≫
    pullbackSymmetry (Spec.map (CommRingCat.ofHom (algebraMap (↑Γ(S, U)) R)))
      (Spec.map (CommRingCat.ofHom (algebraMap ↑Γ(S, U) ↑Γ(X, V))))
he₁ :
  e₁.hom ≫ pullback.fst (Spec.map (Scheme.Hom.appLE f U V hUV)) (Spec.map φ) =
    Spec.map (CommRingCat.ofHom Algebra.TensorProduct.includeRight.toRingHom)
g : Spec (CommRingCat.of (R ⊗[↑Γ(S, U)] ↑Γ(X, V))) ⟶ pullback f (Spec.map φ ≫ IsAffineOpen.fromSpec hU) :=
  e₁.hom ≫
    pullback.map (Spec.map (Scheme.Hom.appLE f U V hUV)) (Spec.map φ) f (Spec.map φ ≫ IsAffineOpen.fromSpec hU)
      (IsAffineOpen.fromSpec hV) (𝟙 (Spec (CommRingCat.of R))) (IsAffineOpen.fromSpec hU) ⋯ ⋯
W₁ : (pullback f (Spec.map φ ≫ IsAffineOpen.fromSpec hU)).Opens := g ''ᵁ PrimeSpectrum.basicOpen e
this✝ : IsFinite (W₁.ι ≫ pullback.snd f (Spec.map φ ≫ IsAffineOpen.fromSpec hU))
this : IsFinite W₁.ι
⊢ ∃ U g,
    Etale g ∧ s ∈ Set.range ⇑g ∧ ∃ V W v, IsCompl V W ∧ IsFinite (V.ι ≫ pullback.snd f g) ∧ (pullback.fst f g) ↑v = x

Tactic:
let W₂ : (pullback f (Spec.map φ ≫ hU.fromSpec)).Opens :=
    ⟨W₁ᶜ, by simpa using W₁.ι.isClosedMap.isClosed_range⟩

Goal state after:
X S : Scheme
f : X ⟶ S
inst✝¹ : LocallyOfFiniteType f
inst✝ : IsSeparated f
x : ↥X
s : ↥S
h : f x = s
hx : Scheme.Hom.QuasiFiniteAt f x
U : TopologicalSpace.Opens ↥S
hU : U ∈ S.affineOpens
hxU : f x ∈ ↑U
V : TopologicalSpace.Opens ↥X
hV : V ∈ X.affineOpens
hxV : x ∈ ↑V
hUV : V ≤ f ⁻¹ᵁ U
this✝⁵ : (CommRingCat.Hom.hom (Scheme.Hom.appLE f U V hUV)).FiniteType
algInst✝ : Algebra ↑Γ(S, U) ↑Γ(X, V) := (CommRingCat.Hom.hom (Scheme.Hom.appLE f U V hUV)).toAlgebra
algebraizeInst✝ : Algebra.FiniteType ↑Γ(S, U) ↑Γ(X, V)
this✝⁴ : (IsAffineOpen.primeIdealOf hV ⟨x, hxV⟩).asIdeal.LiesOver (IsAffineOpen.primeIdealOf hU ⟨f x, hxU⟩).asIdeal
this✝³ : Algebra.QuasiFiniteAt (↑Γ(S, U)) (IsAffineOpen.primeIdealOf hV ⟨x, hxV⟩).asIdeal
R : Type u
w✝⁷ : CommRing R
w✝⁶ : Algebra (↑Γ(S, U)) R
w✝⁵ : Algebra.Etale (↑Γ(S, U)) R
P : Ideal R
w✝⁴ : P.IsPrime
w✝³ : P.LiesOver (IsAffineOpen.primeIdealOf hU ⟨f x, hxU⟩).asIdeal
e : R ⊗[↑Γ(S, U)] ↑Γ(X, V)
w✝² : IsIdempotentElem e
P' : Ideal (R ⊗[↑Γ(S, U)] ↑Γ(X, V))
w✝¹ : P'.IsPrime
w✝ : P'.LiesOver P
hP' : Ideal.comap Algebra.TensorProduct.includeRight.toRingHom P' = (IsAffineOpen.primeIdealOf hV ⟨x, hxV⟩).asIdeal
heP' : e ∉ P'
left✝ : Module.Finite R (Localization.Away e)
this✝² : (algebraMap R (Localization.Away e)).Finite
φ : Γ(S, U) ⟶ CommRingCat.of R := CommRingCat.ofHom (algebraMap (↑Γ(S, U)) R)
hφ : (CommRingCat.Hom.hom φ).Etale
this✝¹ : Etale (Spec.map φ)
e₁ : Spec (CommRingCat.of (R ⊗[↑Γ(S, U)] ↑Γ(X, V))) ≅ pullback (Spec.map (Scheme.Hom.appLE f U V hUV)) (Spec.map φ) :=
  (pullbackSpecIso (↑Γ(S, U)) R ↑Γ(X, V)).symm ≪≫
    pullbackSymmetry (Spec.map (CommRingCat.ofHom (algebraMap (↑Γ(S, U)) R)))
      (Spec.map (CommRingCat.ofHom (algebraMap ↑Γ(S, U) ↑Γ(X, V))))
he₁ :
  e₁.hom ≫ pullback.fst (Spec.map (Scheme.Hom.appLE f U V hUV)) (Spec.map φ) =
    Spec.map (CommRingCat.ofHom Algebra.TensorProduct.includeRight.toRingHom)
g : Spec (CommRingCat.of (R ⊗[↑Γ(S, U)] ↑Γ(X, V))) ⟶ pullback f (Spec.map φ ≫ IsAffineOpen.fromSpec hU) :=
  e₁.hom ≫
    pullback.map (Spec.map (Scheme.Hom.appLE f U V hUV)) (Spec.map φ) f (Spec.map φ ≫ IsAffineOpen.fromSpec hU)
      (IsAffineOpen.fromSpec hV) (𝟙 (Spec (CommRingCat.of R))) (IsAffineOpen.fromSpec hU) ⋯ ⋯
W₁ : (pullback f (Spec.map φ ≫ IsAffineOpen.fromSpec hU)).Opens := g ''ᵁ PrimeSpectrum.basicOpen e
this✝ : IsFinite (W₁.ι ≫ pullback.snd f (Spec.map φ ≫ IsAffineOpen.fromSpec hU))
this : IsFinite W₁.ι
W₂ : (pullback f (Spec.map φ ≫ IsAffineOpen.fromSpec hU)).Opens := { carrier := (↑W₁)ᶜ, is_open' := ⋯ }
⊢ ∃ U g,
    Etale g ∧ s ∈ Set.range ⇑g ∧ ∃ V W v, IsCompl V W ∧ IsFinite (V.ι ≫ pullback.snd f g) ∧ (pullback.fst f g) ↑v = x