-- Mathlib/RingTheory/LocalProperties/Basic.lean
theorem RingHom.OfLocalizationSpanTarget.ofLocalizationSpan
    (hP : RingHom.OfLocalizationSpanTarget @P)
    (hP' : RingHom.StableUnderCompositionWithLocalizationAwaySource @P) :
    RingHom.OfLocalizationSpan @P

Proof state:
P : {R S : Type u} → [inst : CommRing R] → [inst_1 : CommRing S] → (R →+* S) → Prop
hP : OfLocalizationSpanTarget P
hP' : StableUnderCompositionWithLocalizationAwaySource P
R S : Type u
inst✝¹ : CommRing R
inst✝ : CommRing S
f : R →+* S
s : Set R
hs : Ideal.span s = ⊤
hs' : ∀ (r : ↑s), P (Localization.awayMap f ↑r)
⊢ P f

Tactic:
apply_fun Ideal.map f at hs

Result:
P : {R S : Type u} → [inst : CommRing R] → [inst_1 : CommRing S] → (R →+* S) → Prop
hP : OfLocalizationSpanTarget P
hP' : StableUnderCompositionWithLocalizationAwaySource P
R S : Type u
inst✝¹ : CommRing R
inst✝ : CommRing S
f : R →+* S
s : Set R
hs' : ∀ (r : ↑s), P (Localization.awayMap f ↑r)
hs : Ideal.map f (Ideal.span s) = Ideal.map f ⊤
⊢ P f

Proof state:
P : {R S : Type u} → [inst : CommRing R] → [inst_1 : CommRing S] → (R →+* S) → Prop
hP : OfLocalizationSpanTarget P
hP' : StableUnderCompositionWithLocalizationAwaySource P
R S : Type u
inst✝¹ : CommRing R
inst✝ : CommRing S
f : R →+* S
s : Set R
hs' : ∀ (r : ↑s), P (Localization.awayMap f ↑r)
hs : Ideal.map f (Ideal.span s) = Ideal.map f ⊤
⊢ P f

Tactic:
rw [Ideal.map_span, Ideal.map_top] at hs

Result:
P : {R S : Type u} → [inst : CommRing R] → [inst_1 : CommRing S] → (R →+* S) → Prop
hP : OfLocalizationSpanTarget P
hP' : StableUnderCompositionWithLocalizationAwaySource P
R S : Type u
inst✝¹ : CommRing R
inst✝ : CommRing S
f : R →+* S
s : Set R
hs' : ∀ (r : ↑s), P (Localization.awayMap f ↑r)
hs : Ideal.span (⇑f '' s) = ⊤
⊢ P f

Proof state:
P : {R S : Type u} → [inst : CommRing R] → [inst_1 : CommRing S] → (R →+* S) → Prop
hP : OfLocalizationSpanTarget P
hP' : StableUnderCompositionWithLocalizationAwaySource P
R S : Type u
inst✝¹ : CommRing R
inst✝ : CommRing S
f : R →+* S
s : Set R
hs' : ∀ (r : ↑s), P (Localization.awayMap f ↑r)
hs : Ideal.span (⇑f '' s) = ⊤
⊢ ∀ (r : ↑(⇑f '' s)), P ((algebraMap S (Localization.Away ↑r)).comp f)

Tactic:
rintro ⟨_, r, hr, rfl⟩

Result:
case mk.intro.intro
P : {R S : Type u} → [inst : CommRing R] → [inst_1 : CommRing S] → (R →+* S) → Prop
hP : OfLocalizationSpanTarget P
hP' : StableUnderCompositionWithLocalizationAwaySource P
R S : Type u
inst✝¹ : CommRing R
inst✝ : CommRing S
f : R →+* S
s : Set R
hs' : ∀ (r : ↑s), P (Localization.awayMap f ↑r)
hs : Ideal.span (⇑f '' s) = ⊤
r : R
hr : r ∈ s
⊢ P ((algebraMap S (Localization.Away ↑⟨f r, ⋯⟩)).comp f)

Proof state:
case mk.intro.intro
P : {R S : Type u} → [inst : CommRing R] → [inst_1 : CommRing S] → (R →+* S) → Prop
hP : OfLocalizationSpanTarget P
hP' : StableUnderCompositionWithLocalizationAwaySource P
R S : Type u
inst✝¹ : CommRing R
inst✝ : CommRing S
f : R →+* S
s : Set R
hs' : ∀ (r : ↑s), P (Localization.awayMap f ↑r)
hs : Ideal.span (⇑f '' s) = ⊤
r : R
hr : r ∈ s
⊢ P ((algebraMap S (Localization.Away ↑⟨f r, ⋯⟩)).comp f)

Tactic:
rw [← IsLocalization.map_comp (M := Submonoid.powers r) (S := Localization.Away r)
  (T := Submonoid.powers (f r))]

Result:
case mk.intro.intro
P : {R S : Type u} → [inst : CommRing R] → [inst_1 : CommRing S] → (R →+* S) → Prop
hP : OfLocalizationSpanTarget P
hP' : StableUnderCompositionWithLocalizationAwaySource P
R S : Type u
inst✝¹ : CommRing R
inst✝ : CommRing S
f : R →+* S
s : Set R
hs' : ∀ (r : ↑s), P (Localization.awayMap f ↑r)
hs : Ideal.span (⇑f '' s) = ⊤
r : R
hr : r ∈ s
⊢ P ((IsLocalization.map (Localization.Away ↑⟨f r, ⋯⟩) f ?mk.intro.intro).comp (algebraMap R (Localization.Away r)))

case mk.intro.intro
P : {R S : Type u} → [inst : CommRing R] → [inst_1 : CommRing S] → (R →+* S) → Prop
hP : OfLocalizationSpanTarget P
hP' : StableUnderCompositionWithLocalizationAwaySource P
R S : Type u
inst✝¹ : CommRing R
inst✝ : CommRing S
f : R →+* S
s : Set R
hs' : ∀ (r : ↑s), P (Localization.awayMap f ↑r)
hs : Ideal.span (⇑f '' s) = ⊤
r : R
hr : r ∈ s
⊢ Submonoid.powers r ≤ Submonoid.comap f (Submonoid.powers (f r))

Proof state:
case mk.intro.intro.a
P : {R S : Type u} → [inst : CommRing R] → [inst_1 : CommRing S] → (R →+* S) → Prop
hP : OfLocalizationSpanTarget P
hP' : StableUnderCompositionWithLocalizationAwaySource P
R S : Type u
inst✝¹ : CommRing R
inst✝ : CommRing S
f : R →+* S
s : Set R
hs' : ∀ (r : ↑s), P (Localization.awayMap f ↑r)
hs : Ideal.span (⇑f '' s) = ⊤
r : R
hr : r ∈ s
⊢ P (IsLocalization.map (Localization.Away ↑⟨f r, ⋯⟩) f ?mk.intro.intro)

Tactic:
exact hs' ⟨r, hr⟩

Result:
no goals

Proof state:
case mk.intro.intro
P : {R S : Type u} → [inst : CommRing R] → [inst_1 : CommRing S] → (R →+* S) → Prop
hP : OfLocalizationSpanTarget P
hP' : StableUnderCompositionWithLocalizationAwaySource P
R S : Type u
inst✝¹ : CommRing R
inst✝ : CommRing S
f : R →+* S
s : Set R
hs' : ∀ (r : ↑s), P (Localization.awayMap f ↑r)
hs : Ideal.span (⇑f '' s) = ⊤
r : R
hr : r ∈ s
⊢ P ((IsLocalization.map (Localization.Away ↑⟨f r, ⋯⟩) f ?mk.intro.intro).comp (algebraMap R (Localization.Away r)))

Tactic:
apply hP' _ r

Result:
case mk.intro.intro.a
P : {R S : Type u} → [inst : CommRing R] → [inst_1 : CommRing S] → (R →+* S) → Prop
hP : OfLocalizationSpanTarget P
hP' : StableUnderCompositionWithLocalizationAwaySource P
R S : Type u
inst✝¹ : CommRing R
inst✝ : CommRing S
f : R →+* S
s : Set R
hs' : ∀ (r : ↑s), P (Localization.awayMap f ↑r)
hs : Ideal.span (⇑f '' s) = ⊤
r : R
hr : r ∈ s
⊢ P (IsLocalization.map (Localization.Away ↑⟨f r, ⋯⟩) f ?mk.intro.intro)

Proof state:
P : {R S : Type u} → [inst : CommRing R] → [inst_1 : CommRing S] → (R →+* S) → Prop
hP : OfLocalizationSpanTarget P
hP' : StableUnderCompositionWithLocalizationAwaySource P
R S : Type u
inst✝¹ : CommRing R
inst✝ : CommRing S
f : R →+* S
s : Set R
hs' : ∀ (r : ↑s), P (Localization.awayMap f ↑r)
hs : Ideal.span (⇑f '' s) = ⊤
⊢ P f

Tactic:
apply hP _ _ hs

Result:
P : {R S : Type u} → [inst : CommRing R] → [inst_1 : CommRing S] → (R →+* S) → Prop
hP : OfLocalizationSpanTarget P
hP' : StableUnderCompositionWithLocalizationAwaySource P
R S : Type u
inst✝¹ : CommRing R
inst✝ : CommRing S
f : R →+* S
s : Set R
hs' : ∀ (r : ↑s), P (Localization.awayMap f ↑r)
hs : Ideal.span (⇑f '' s) = ⊤
⊢ ∀ (r : ↑(⇑f '' s)), P ((algebraMap S (Localization.Away ↑r)).comp f)

Proof state:
P : {R S : Type u} → [inst : CommRing R] → [inst_1 : CommRing S] → (R →+* S) → Prop
hP : OfLocalizationSpanTarget P
hP' : StableUnderCompositionWithLocalizationAwaySource P
⊢ OfLocalizationSpan P

Tactic:
introv R hs hs'

Result:
P : {R S : Type u} → [inst : CommRing R] → [inst_1 : CommRing S] → (R →+* S) → Prop
hP : OfLocalizationSpanTarget P
hP' : StableUnderCompositionWithLocalizationAwaySource P
R S : Type u
inst✝¹ : CommRing R
inst✝ : CommRing S
f : R →+* S
s : Set R
hs : Ideal.span s = ⊤
hs' : ∀ (r : ↑s), P (Localization.awayMap f ↑r)
⊢ P f