-- Mathlib/RingTheory/RingHom/Locally.lean
/-- If `P` is preserved by localizations, then so is `Locally P`. -/
lemma locally_localizationPreserves (hPl : LocalizationPreserves P) :
    LocalizationPreserves (Locally P)

Proof state:
P : {R S : Type u} → [inst : CommRing R] → [inst_1 : CommRing S] → (R →+* S) → Prop
hPl : LocalizationPreserves fun {R S} [CommRing R] [CommRing S] => P
R S : Type u
inst✝⁷ : CommRing R
inst✝⁶ : CommRing S
f : R →+* S
M : Submonoid R
R' S' : Type u
inst✝⁵ : CommRing R'
inst✝⁴ : CommRing S'
inst✝³ : Algebra R R'
inst✝² : Algebra S S'
inst✝¹ : IsLocalization M R'
inst✝ : IsLocalization (Submonoid.map f M) S'
hf : Locally (fun {R S} [CommRing R] [CommRing S] => P) f
⊢ Locally (fun {R S} [CommRing R] [CommRing S] => P) (IsLocalization.map S' f ⋯)

Tactic:
obtain ⟨s, hsone, hs⟩ := hf

Result:
case intro.intro
P : {R S : Type u} → [inst : CommRing R] → [inst_1 : CommRing S] → (R →+* S) → Prop
hPl : LocalizationPreserves fun {R S} [CommRing R] [CommRing S] => P
R S : Type u
inst✝⁷ : CommRing R
inst✝⁶ : CommRing S
f : R →+* S
M : Submonoid R
R' S' : Type u
inst✝⁵ : CommRing R'
inst✝⁴ : CommRing S'
inst✝³ : Algebra R R'
inst✝² : Algebra S S'
inst✝¹ : IsLocalization M R'
inst✝ : IsLocalization (Submonoid.map f M) S'
s : Set S
hsone : Ideal.span s = ⊤
hs : ∀ t ∈ s, (fun {R S} [CommRing R] [CommRing S] => P) ((algebraMap S (Localization.Away t)).comp f)
⊢ Locally (fun {R S} [CommRing R] [CommRing S] => P) (IsLocalization.map S' f ⋯)

Proof state:
case intro.intro
P : {R S : Type u} → [inst : CommRing R] → [inst_1 : CommRing S] → (R →+* S) → Prop
hPl : LocalizationPreserves fun {R S} [CommRing R] [CommRing S] => P
R S : Type u
inst✝⁷ : CommRing R
inst✝⁶ : CommRing S
f : R →+* S
M : Submonoid R
R' S' : Type u
inst✝⁵ : CommRing R'
inst✝⁴ : CommRing S'
inst✝³ : Algebra R R'
inst✝² : Algebra S S'
inst✝¹ : IsLocalization M R'
inst✝ : IsLocalization (Submonoid.map f M) S'
s : Set S
hsone : Ideal.span s = ⊤
hs : ∀ t ∈ s, (fun {R S} [CommRing R] [CommRing S] => P) ((algebraMap S (Localization.Away t)).comp f)
Mₐ : (a : ↑s) → Submonoid (Localization.Away ↑a) :=
  fun a => Submonoid.map (algebraMap S (Localization.Away ↑a)) (Submonoid.map f M)
Sₐ : ↑s → Type u := fun a => Localization (Mₐ a)
hM : ∀ (a : ↑s), Submonoid.map ((algebraMap S (Localization.Away ↑a)).comp f) M = Mₐ a
this✝ : ∀ (a : ↑s), IsLocalization (Submonoid.map ((algebraMap S (Localization.Away ↑a)).comp f) M) (Sₐ a)
this : ∀ (a : ↑s), IsLocalization (Algebra.algebraMapSubmonoid (Localization.Away ↑a) (Submonoid.map f M)) (Sₐ a)
⊢ ∃ ι s,
    ∃ (_ : Ideal.span (Set.range s) = ⊤),
      ∃ Sₜ x x_1,
        ∃ (_ : ∀ (i : ι), IsLocalization.Away (s i) (Sₜ i)),
          ∀ (i : ι), P ((algebraMap S' (Sₜ i)).comp (IsLocalization.map S' f ⋯))

Tactic:
letI (a : s) : Algebra S' (Sₐ a) :=
  (IsLocalization.map (Sₐ a) (algebraMap S (Localization.Away a.val))
    (M.map f).le_comap_map).toAlgebra

Result:
case intro.intro
P : {R S : Type u} → [inst : CommRing R] → [inst_1 : CommRing S] → (R →+* S) → Prop
hPl : LocalizationPreserves fun {R S} [CommRing R] [CommRing S] => P
R S : Type u
inst✝⁷ : CommRing R
inst✝⁶ : CommRing S
f : R →+* S
M : Submonoid R
R' S' : Type u
inst✝⁵ : CommRing R'
inst✝⁴ : CommRing S'
inst✝³ : Algebra R R'
inst✝² : Algebra S S'
inst✝¹ : IsLocalization M R'
inst✝ : IsLocalization (Submonoid.map f M) S'
s : Set S
hsone : Ideal.span s = ⊤
hs : ∀ t ∈ s, (fun {R S} [CommRing R] [CommRing S] => P) ((algebraMap S (Localization.Away t)).comp f)
Mₐ : (a : ↑s) → Submonoid (Localization.Away ↑a) :=
  fun a => Submonoid.map (algebraMap S (Localization.Away ↑a)) (Submonoid.map f M)
Sₐ : ↑s → Type u := fun a => Localization (Mₐ a)
hM : ∀ (a : ↑s), Submonoid.map ((algebraMap S (Localization.Away ↑a)).comp f) M = Mₐ a
this✝¹ : ∀ (a : ↑s), IsLocalization (Submonoid.map ((algebraMap S (Localization.Away ↑a)).comp f) M) (Sₐ a)
this✝ : ∀ (a : ↑s), IsLocalization (Algebra.algebraMapSubmonoid (Localization.Away ↑a) (Submonoid.map f M)) (Sₐ a)
this : (a : ↑s) → Algebra S' (Sₐ a) :=
  fun a => (IsLocalization.map (Sₐ a) (algebraMap S (Localization.Away ↑a)) ⋯).toAlgebra
⊢ ∃ ι s,
    ∃ (_ : Ideal.span (Set.range s) = ⊤),
      ∃ Sₜ x x_1,
        ∃ (_ : ∀ (i : ι), IsLocalization.Away (s i) (Sₜ i)),
          ∀ (i : ι), P ((algebraMap S' (Sₜ i)).comp (IsLocalization.map S' f ⋯))

Proof state:
case intro.intro.refine_3.a
P : {R S : Type u} → [inst : CommRing R] → [inst_1 : CommRing S] → (R →+* S) → Prop
hPl : LocalizationPreserves fun {R S} [CommRing R] [CommRing S] => P
R S : Type u
inst✝⁷ : CommRing R
inst✝⁶ : CommRing S
f : R →+* S
M : Submonoid R
R' S' : Type u
inst✝⁵ : CommRing R'
inst✝⁴ : CommRing S'
inst✝³ : Algebra R R'
inst✝² : Algebra S S'
inst✝¹ : IsLocalization M R'
inst✝ : IsLocalization (Submonoid.map f M) S'
s : Set S
hsone : Ideal.span s = ⊤
hs : ∀ t ∈ s, (fun {R S} [CommRing R] [CommRing S] => P) ((algebraMap S (Localization.Away t)).comp f)
Mₐ : (a : ↑s) → Submonoid (Localization.Away ↑a) :=
  fun a => Submonoid.map (algebraMap S (Localization.Away ↑a)) (Submonoid.map f M)
Sₐ : ↑s → Type u := fun a => Localization (Mₐ a)
hM : ∀ (a : ↑s), Submonoid.map ((algebraMap S (Localization.Away ↑a)).comp f) M = Mₐ a
this✝² : ∀ (a : ↑s), IsLocalization (Submonoid.map ((algebraMap S (Localization.Away ↑a)).comp f) M) (Sₐ a)
this✝¹ : ∀ (a : ↑s), IsLocalization (Algebra.algebraMapSubmonoid (Localization.Away ↑a) (Submonoid.map f M)) (Sₐ a)
this✝ : (a : ↑s) → Algebra S' (Sₐ a) :=
  fun a => (IsLocalization.map (Sₐ a) (algebraMap S (Localization.Away ↑a)) ⋯).toAlgebra
this : ∀ (a : ↑s), IsScalarTower S S' (Sₐ a)
a : ↑s
⊢ P ((algebraMap S (Localization.Away ↑a)).comp f)

Tactic:
exact hs a.val a.property

Result:
no goals

Proof state:
case intro.intro
P : {R S : Type u} → [inst : CommRing R] → [inst_1 : CommRing S] → (R →+* S) → Prop
hPl : LocalizationPreserves fun {R S} [CommRing R] [CommRing S] => P
R S : Type u
inst✝⁷ : CommRing R
inst✝⁶ : CommRing S
f : R →+* S
M : Submonoid R
R' S' : Type u
inst✝⁵ : CommRing R'
inst✝⁴ : CommRing S'
inst✝³ : Algebra R R'
inst✝² : Algebra S S'
inst✝¹ : IsLocalization M R'
inst✝ : IsLocalization (Submonoid.map f M) S'
s : Set S
hsone : Ideal.span s = ⊤
hs : ∀ t ∈ s, (fun {R S} [CommRing R] [CommRing S] => P) ((algebraMap S (Localization.Away t)).comp f)
⊢ Locally (fun {R S} [CommRing R] [CommRing S] => P) (IsLocalization.map S' f ⋯)

Tactic:
rw [locally_iff_exists hPl.away.respectsIso]

Result:
case intro.intro
P : {R S : Type u} → [inst : CommRing R] → [inst_1 : CommRing S] → (R →+* S) → Prop
hPl : LocalizationPreserves fun {R S} [CommRing R] [CommRing S] => P
R S : Type u
inst✝⁷ : CommRing R
inst✝⁶ : CommRing S
f : R →+* S
M : Submonoid R
R' S' : Type u
inst✝⁵ : CommRing R'
inst✝⁴ : CommRing S'
inst✝³ : Algebra R R'
inst✝² : Algebra S S'
inst✝¹ : IsLocalization M R'
inst✝ : IsLocalization (Submonoid.map f M) S'
s : Set S
hsone : Ideal.span s = ⊤
hs : ∀ t ∈ s, (fun {R S} [CommRing R] [CommRing S] => P) ((algebraMap S (Localization.Away t)).comp f)
⊢ ∃ ι s,
    ∃ (_ : Ideal.span (Set.range s) = ⊤),
      ∃ Sₜ x x_1,
        ∃ (_ : ∀ (i : ι), IsLocalization.Away (s i) (Sₜ i)),
          ∀ (i : ι), P ((algebraMap S' (Sₜ i)).comp (IsLocalization.map S' f ⋯))