-- Mathlib/CategoryTheory/Localization/StructuredArrow.lean
@[elab_as_elim]
lemma induction_costructuredArrow
    (hP₀ : P (CostructuredArrow.mk (𝟙 (L.obj Y))))
    (hP₁ : ∀ ⦃X₁ X₂ : C⦄ (f : X₁ ⟶ X₂) (φ : L.obj X₂ ⟶ L.obj Y),
      P (CostructuredArrow.mk φ) → P (CostructuredArrow.mk (L.map f ≫ φ)))
    (hP₂ : ∀ ⦃X₁ X₂ : C⦄ (w : X₁ ⟶ X₂) (hw : W w) (φ : L.obj X₁ ⟶ L.obj Y),
      P (CostructuredArrow.mk φ) → P (CostructuredArrow.mk ((isoOfHom L W w hw).inv ≫ φ)))
    (g : CostructuredArrow L (L.obj Y)) : P g

Proof state:
case hP₂
C : Type u_1
D : Type u_2
inst✝² : Category.{u_4, u_1} C
inst✝¹ : Category.{u_5, u_2} D
L : C ⥤ D
W : MorphismProperty C
inst✝ : L.IsLocalization W
Y : C
P : CostructuredArrow L (L.obj Y) → Prop
hP₀ : P (CostructuredArrow.mk (𝟙 (L.obj Y)))
hP₁ :
  ∀ ⦃X₁ X₂ : C⦄ (f : X₁ ⟶ X₂) (φ : L.obj X₂ ⟶ L.obj Y),
    P (CostructuredArrow.mk φ) → P (CostructuredArrow.mk (L.map f ≫ φ))
hP₂ :
  ∀ ⦃X₁ X₂ : C⦄ (w : X₁ ⟶ X₂) (hw : W w) (φ : L.obj X₁ ⟶ L.obj Y),
    P (CostructuredArrow.mk φ) → P (CostructuredArrow.mk ((isoOfHom L W w hw).inv ≫ φ))
g : CostructuredArrow L (L.obj Y)
g' : StructuredArrow (op ((Functor.fromPUnit (L.obj Y)).obj g.right)) L.op := StructuredArrow.mk g.hom.op
Y₁✝ Y₂✝ : Cᵒᵖ
w : Y₁✝ ⟶ Y₂✝
hw : W.op w
φ : L.op.obj (op Y) ⟶ L.op.obj Y₂✝
hφ : P (CostructuredArrow.mk (StructuredArrow.mk φ).hom.unop)
⊢ P (CostructuredArrow.mk (StructuredArrow.mk (φ ≫ (isoOfHom L.op W.op w hw).inv)).hom.unop)

Tactic:
simpa [isoOfHom_op_inv L W w hw] using hP₂ w.unop hw φ.unop hφ

Result:
no goals

Proof state:
case hP₁
C : Type u_1
D : Type u_2
inst✝² : Category.{u_4, u_1} C
inst✝¹ : Category.{u_5, u_2} D
L : C ⥤ D
W : MorphismProperty C
inst✝ : L.IsLocalization W
Y : C
P : CostructuredArrow L (L.obj Y) → Prop
hP₀ : P (CostructuredArrow.mk (𝟙 (L.obj Y)))
hP₁ :
  ∀ ⦃X₁ X₂ : C⦄ (f : X₁ ⟶ X₂) (φ : L.obj X₂ ⟶ L.obj Y),
    P (CostructuredArrow.mk φ) → P (CostructuredArrow.mk (L.map f ≫ φ))
hP₂ :
  ∀ ⦃X₁ X₂ : C⦄ (w : X₁ ⟶ X₂) (hw : W w) (φ : L.obj X₁ ⟶ L.obj Y),
    P (CostructuredArrow.mk φ) → P (CostructuredArrow.mk ((isoOfHom L W w hw).inv ≫ φ))
g : CostructuredArrow L (L.obj Y)
g' : StructuredArrow (op ((Functor.fromPUnit (L.obj Y)).obj g.right)) L.op := StructuredArrow.mk g.hom.op
Y₁✝ Y₂✝ : Cᵒᵖ
f : Y₁✝ ⟶ Y₂✝
φ : L.op.obj (op Y) ⟶ L.op.obj Y₁✝
hφ : P (CostructuredArrow.mk (StructuredArrow.mk φ).hom.unop)
⊢ P (CostructuredArrow.mk (StructuredArrow.mk (φ ≫ L.op.map f)).hom.unop)

Tactic:
exact hP₁ f.unop φ.unop hφ

Result:
no goals

Proof state:
case hP₀
C : Type u_1
D : Type u_2
inst✝² : Category.{u_4, u_1} C
inst✝¹ : Category.{u_5, u_2} D
L : C ⥤ D
W : MorphismProperty C
inst✝ : L.IsLocalization W
Y : C
P : CostructuredArrow L (L.obj Y) → Prop
hP₀ : P (CostructuredArrow.mk (𝟙 (L.obj Y)))
hP₁ :
  ∀ ⦃X₁ X₂ : C⦄ (f : X₁ ⟶ X₂) (φ : L.obj X₂ ⟶ L.obj Y),
    P (CostructuredArrow.mk φ) → P (CostructuredArrow.mk (L.map f ≫ φ))
hP₂ :
  ∀ ⦃X₁ X₂ : C⦄ (w : X₁ ⟶ X₂) (hw : W w) (φ : L.obj X₁ ⟶ L.obj Y),
    P (CostructuredArrow.mk φ) → P (CostructuredArrow.mk ((isoOfHom L W w hw).inv ≫ φ))
g : CostructuredArrow L (L.obj Y)
g' : StructuredArrow (op ((Functor.fromPUnit (L.obj Y)).obj g.right)) L.op := StructuredArrow.mk g.hom.op
⊢ P (CostructuredArrow.mk (StructuredArrow.mk (𝟙 (L.op.obj (op Y)))).hom.unop)

Tactic:
exact hP₀

Result:
no goals

Proof state:
C : Type u_1
D : Type u_2
inst✝² : Category.{u_4, u_1} C
inst✝¹ : Category.{u_5, u_2} D
L : C ⥤ D
W : MorphismProperty C
inst✝ : L.IsLocalization W
Y : C
P : CostructuredArrow L (L.obj Y) → Prop
hP₀ : P (CostructuredArrow.mk (𝟙 (L.obj Y)))
hP₁ :
  ∀ ⦃X₁ X₂ : C⦄ (f : X₁ ⟶ X₂) (φ : L.obj X₂ ⟶ L.obj Y),
    P (CostructuredArrow.mk φ) → P (CostructuredArrow.mk (L.map f ≫ φ))
hP₂ :
  ∀ ⦃X₁ X₂ : C⦄ (w : X₁ ⟶ X₂) (hw : W w) (φ : L.obj X₁ ⟶ L.obj Y),
    P (CostructuredArrow.mk φ) → P (CostructuredArrow.mk ((isoOfHom L W w hw).inv ≫ φ))
g : CostructuredArrow L (L.obj Y)
g' : StructuredArrow (op ((Functor.fromPUnit (L.obj Y)).obj g.right)) L.op := StructuredArrow.mk g.hom.op
⊢ P g

Tactic:
show P (CostructuredArrow.mk g'.hom.unop)

Result:
C : Type u_1
D : Type u_2
inst✝² : Category.{u_4, u_1} C
inst✝¹ : Category.{u_5, u_2} D
L : C ⥤ D
W : MorphismProperty C
inst✝ : L.IsLocalization W
Y : C
P : CostructuredArrow L (L.obj Y) → Prop
hP₀ : P (CostructuredArrow.mk (𝟙 (L.obj Y)))
hP₁ :
  ∀ ⦃X₁ X₂ : C⦄ (f : X₁ ⟶ X₂) (φ : L.obj X₂ ⟶ L.obj Y),
    P (CostructuredArrow.mk φ) → P (CostructuredArrow.mk (L.map f ≫ φ))
hP₂ :
  ∀ ⦃X₁ X₂ : C⦄ (w : X₁ ⟶ X₂) (hw : W w) (φ : L.obj X₁ ⟶ L.obj Y),
    P (CostructuredArrow.mk φ) → P (CostructuredArrow.mk ((isoOfHom L W w hw).inv ≫ φ))
g : CostructuredArrow L (L.obj Y)
g' : StructuredArrow (op ((Functor.fromPUnit (L.obj Y)).obj g.right)) L.op := StructuredArrow.mk g.hom.op
⊢ P (CostructuredArrow.mk g'.hom.unop)

Proof state:
C : Type u_1
D : Type u_2
inst✝² : Category.{u_4, u_1} C
inst✝¹ : Category.{u_5, u_2} D
L : C ⥤ D
W : MorphismProperty C
inst✝ : L.IsLocalization W
Y : C
P : CostructuredArrow L (L.obj Y) → Prop
hP₀ : P (CostructuredArrow.mk (𝟙 (L.obj Y)))
hP₁ :
  ∀ ⦃X₁ X₂ : C⦄ (f : X₁ ⟶ X₂) (φ : L.obj X₂ ⟶ L.obj Y),
    P (CostructuredArrow.mk φ) → P (CostructuredArrow.mk (L.map f ≫ φ))
hP₂ :
  ∀ ⦃X₁ X₂ : C⦄ (w : X₁ ⟶ X₂) (hw : W w) (φ : L.obj X₁ ⟶ L.obj Y),
    P (CostructuredArrow.mk φ) → P (CostructuredArrow.mk ((isoOfHom L W w hw).inv ≫ φ))
g : CostructuredArrow L (L.obj Y)
⊢ P g

Tactic:
let g' := StructuredArrow.mk (T := L.op) (Y := op g.left) g.hom.op

Result:
C : Type u_1
D : Type u_2
inst✝² : Category.{u_4, u_1} C
inst✝¹ : Category.{u_5, u_2} D
L : C ⥤ D
W : MorphismProperty C
inst✝ : L.IsLocalization W
Y : C
P : CostructuredArrow L (L.obj Y) → Prop
hP₀ : P (CostructuredArrow.mk (𝟙 (L.obj Y)))
hP₁ :
  ∀ ⦃X₁ X₂ : C⦄ (f : X₁ ⟶ X₂) (φ : L.obj X₂ ⟶ L.obj Y),
    P (CostructuredArrow.mk φ) → P (CostructuredArrow.mk (L.map f ≫ φ))
hP₂ :
  ∀ ⦃X₁ X₂ : C⦄ (w : X₁ ⟶ X₂) (hw : W w) (φ : L.obj X₁ ⟶ L.obj Y),
    P (CostructuredArrow.mk φ) → P (CostructuredArrow.mk ((isoOfHom L W w hw).inv ≫ φ))
g : CostructuredArrow L (L.obj Y)
g' : StructuredArrow (op ((Functor.fromPUnit (L.obj Y)).obj g.right)) L.op := StructuredArrow.mk g.hom.op
⊢ P g

Proof state:
C : Type u_1
D : Type u_2
inst✝² : Category.{u_4, u_1} C
inst✝¹ : Category.{u_5, u_2} D
L : C ⥤ D
W : MorphismProperty C
inst✝ : L.IsLocalization W
Y : C
P : CostructuredArrow L (L.obj Y) → Prop
hP₀ : P (CostructuredArrow.mk (𝟙 (L.obj Y)))
hP₁ :
  ∀ ⦃X₁ X₂ : C⦄ (f : X₁ ⟶ X₂) (φ : L.obj X₂ ⟶ L.obj Y),
    P (CostructuredArrow.mk φ) → P (CostructuredArrow.mk (L.map f ≫ φ))
hP₂ :
  ∀ ⦃X₁ X₂ : C⦄ (w : X₁ ⟶ X₂) (hw : W w) (φ : L.obj X₁ ⟶ L.obj Y),
    P (CostructuredArrow.mk φ) → P (CostructuredArrow.mk ((isoOfHom L W w hw).inv ≫ φ))
g : CostructuredArrow L (L.obj Y)
g' : StructuredArrow (op ((Functor.fromPUnit (L.obj Y)).obj g.right)) L.op := StructuredArrow.mk g.hom.op
⊢ P (CostructuredArrow.mk g'.hom.unop)

Tactic:
induction g' using induction_structuredArrow L.op W.op with
| hP₀ => exact hP₀
| hP₁ f φ hφ => exact hP₁ f.unop φ.unop hφ
| hP₂ w hw φ hφ => simpa [isoOfHom_op_inv L W w hw] using hP₂ w.unop hw φ.unop hφ

Result:
no goals