Module: Mathlib.AlgebraicGeometry.AffineTransitionLimit

Goal state before:
pp: case inr
I : Type u
inst✝⁵ : Category.{u, u} I
inst✝⁴ : IsCofiltered I
R : CommRingCat
inst✝³ : IsAffine (Spec R)
S : CommRingCat
inst✝² : IsAffine (Spec S)
φ : R ⟶ S
inst✝¹ : LocallyOfFinitePresentation (Spec.map φ)
D : I ⥤ CommRingCatᵒᵖ
c : Cone (D ⋙ Scheme.Spec)
hc : IsLimit c
inst✝ : ∀ (i : I), IsAffine ((D ⋙ Scheme.Spec).obj i)
a : c.pt ⟶ Spec S
e : ((Functor.const Iᵒᵖ).obj R).rightOp ⋙ Scheme.Spec ≅ (Functor.const I).obj (Spec R) :=
  NatIso.ofComponents (fun x ↦ Iso.refl ((((Functor.const Iᵒᵖ).obj R).rightOp ⋙ Scheme.Spec).obj x)) ⋯
t : (Functor.const Iᵒᵖ).obj R ⟶ D.leftOp
ha : c.π ≫ Functor.whiskerRight (NatTrans.rightOp t) Scheme.Spec ≫ e.hom = (Functor.const I).map (a ≫ Spec.map φ)
this :
  ∀ (c : Cone (D ⋙ Scheme.Spec)) (hc : IsLimit c) (a : c.pt ⟶ Spec S),
    c.π ≫ Functor.whiskerRight (NatTrans.rightOp t) Scheme.Spec ≫ e.hom = (Functor.const I).map (a ≫ Spec.map φ) →
      (∃ c', c = Scheme.Spec.mapCone (coneOfCoconeLeftOp c')) →
        ∃ i g,
          c.π.app i ≫ g = a ∧ g ≫ Spec.map φ = (Functor.whiskerRight (NatTrans.rightOp t) Scheme.Spec ≫ e.hom).app i
hc' : ¬∃ c', c = Scheme.Spec.mapCone (coneOfCoconeLeftOp c')
⊢ ∃ i g, c.π.app i ≫ g = a ∧ g ≫ Spec.map φ = (Functor.whiskerRight (NatTrans.rightOp t) Scheme.Spec ≫ e.hom).app i

pp: I : Type u
inst✝⁵ : Category.{u, u} I
inst✝⁴ : IsCofiltered I
R : CommRingCat
inst✝³ : IsAffine (Spec R)
S : CommRingCat
inst✝² : IsAffine (Spec S)
φ : R ⟶ S
inst✝¹ : LocallyOfFinitePresentation (Spec.map φ)
D : I ⥤ CommRingCatᵒᵖ
inst✝ : ∀ (i : I), IsAffine ((D ⋙ Scheme.Spec).obj i)
e : ((Functor.const Iᵒᵖ).obj R).rightOp ⋙ Scheme.Spec ≅ (Functor.const I).obj (Spec R) :=
  NatIso.ofComponents (fun x ↦ Iso.refl ((((Functor.const Iᵒᵖ).obj R).rightOp ⋙ Scheme.Spec).obj x)) ⋯
t : (Functor.const Iᵒᵖ).obj R ⟶ D.leftOp
c : Cone (D ⋙ Scheme.Spec)
hc : IsLimit c
a : c.pt ⟶ Spec S
ha : c.π ≫ Functor.whiskerRight (NatTrans.rightOp t) Scheme.Spec ≫ e.hom = (Functor.const I).map (a ≫ Spec.map φ)
hc' : ∃ c', c = Scheme.Spec.mapCone (coneOfCoconeLeftOp c')
⊢ ∃ i g, c.π.app i ≫ g = a ∧ g ≫ Spec.map φ = (Functor.whiskerRight (NatTrans.rightOp t) Scheme.Spec ≫ e.hom).app i

Tactic:
· have inst : IsAffine c.pt := isAffine_of_isLimit _ hc
    let e' : (D ⋙ Scheme.Spec).op ⋙ Γ ≅ D.leftOp := D.leftOp.isoWhiskerLeft SpecΓIdentity
    let c' := coneOfCoconeLeftOp ((Cocone.precompose e'.inv).obj (Γ.mapCocone c.op))
    have inst : ∀ i, IsAffine ((D ⋙ Scheme.Spec).op.obj i).unop := by dsimp; infer_instance
    obtain ⟨i, f, hf⟩ := this (Scheme.Spec.mapCone c') (isLimitOfPreserves _
      (isLimitConeOfCoconeLeftOp _ ((IsColimit.precomposeHomEquiv e'.symm _).symm
        (isColimitOfPreserves _ hc.op)))) (c.pt.isoSpec.inv ≫ a) (by
        ext i
        have : c.π.app i ≫ Spec.map (t.app (.op i)) = a ≫ Spec.map φ := by
          simpa using! congr((($ha).app i))
        simp [c', e, e', ← this, Iso.eq_inv_comp, isoSpec_hom_naturality_assoc]) ⟨_, rfl⟩
    refine ⟨i, f, ?_⟩
    simpa [Iso.eq_inv_comp, c', isoSpec_hom_naturality_assoc, e'] using! hf

Goal state after:
I : Type u
inst✝⁵ : Category.{u, u} I
inst✝⁴ : IsCofiltered I
R : CommRingCat
inst✝³ : IsAffine (Spec R)
S : CommRingCat
inst✝² : IsAffine (Spec S)
φ : R ⟶ S
inst✝¹ : LocallyOfFinitePresentation (Spec.map φ)
D : I ⥤ CommRingCatᵒᵖ
inst✝ : ∀ (i : I), IsAffine ((D ⋙ Scheme.Spec).obj i)
e : ((Functor.const Iᵒᵖ).obj R).rightOp ⋙ Scheme.Spec ≅ (Functor.const I).obj (Spec R) :=
  NatIso.ofComponents (fun x ↦ Iso.refl ((((Functor.const Iᵒᵖ).obj R).rightOp ⋙ Scheme.Spec).obj x)) ⋯
t : (Functor.const Iᵒᵖ).obj R ⟶ D.leftOp
c : Cone (D ⋙ Scheme.Spec)
hc : IsLimit c
a : c.pt ⟶ Spec S
ha : c.π ≫ Functor.whiskerRight (NatTrans.rightOp t) Scheme.Spec ≫ e.hom = (Functor.const I).map (a ≫ Spec.map φ)
hc' : ∃ c', c = Scheme.Spec.mapCone (coneOfCoconeLeftOp c')
⊢ ∃ i g, c.π.app i ≫ g = a ∧ g ≫ Spec.map φ = (Functor.whiskerRight (NatTrans.rightOp t) Scheme.Spec ≫ e.hom).app i