-- Mathlib/RingTheory/RingHom/Locally.lean
/-- `Locally P` is local on the target. -/
lemma locally_ofLocalizationSpanTarget (hP : RespectsIso P) :
    OfLocalizationSpanTarget (Locally P)

Proof state:
P : {R S : Type u} → [inst : CommRing R] → [inst_1 : CommRing S] → (R →+* S) → Prop
hP : RespectsIso fun {R S} [CommRing R] [CommRing S] => P
R S : Type u
inst✝¹ : CommRing R
inst✝ : CommRing S
f : R →+* S
s : Set S
hsone : Ideal.span s = ⊤
t : (r : ↑s) → Set (Localization.Away ↑r)
htone : ∀ (r : ↑s), Ideal.span (t r) = ⊤
ht :
  ∀ (r : ↑s),
    ∀ t_1 ∈ t r,
      (fun {R S} [CommRing R] [CommRing S] => P)
        ((algebraMap (Localization.Away ↑r) (Localization.Away t_1)).comp
          ((algebraMap S (Localization.Away ↑r)).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 f)

Tactic:
refine ⟨(a : s) × t a, IsLocalization.Away.mulNumerator s t,
    IsLocalization.Away.span_range_mulNumerator_eq_top hsone htone,
    fun ⟨a, b⟩ ↦ Localization.Away b.val, inferInstance, inferInstance, fun ⟨a, b⟩ ↦ ?_, ?_⟩

Result:
case refine_1
P : {R S : Type u} → [inst : CommRing R] → [inst_1 : CommRing S] → (R →+* S) → Prop
hP : RespectsIso fun {R S} [CommRing R] [CommRing S] => P
R S : Type u
inst✝¹ : CommRing R
inst✝ : CommRing S
f : R →+* S
s : Set S
hsone : Ideal.span s = ⊤
t : (r : ↑s) → Set (Localization.Away ↑r)
htone : ∀ (r : ↑s), Ideal.span (t r) = ⊤
ht :
  ∀ (r : ↑s),
    ∀ t_1 ∈ t r,
      (fun {R S} [CommRing R] [CommRing S] => P)
        ((algebraMap (Localization.Away ↑r) (Localization.Away t_1)).comp
          ((algebraMap S (Localization.Away ↑r)).comp f))
x✝ : (a : ↑s) × ↑(t a)
a : ↑s
b : ↑(t a)
⊢ IsLocalization.Away (IsLocalization.Away.mulNumerator s t ⟨a, b⟩)
    ((fun x =>
        match x with
        | ⟨a, b⟩ => Localization.Away ↑b)
      ⟨a, b⟩)

case refine_2
P : {R S : Type u} → [inst : CommRing R] → [inst_1 : CommRing S] → (R →+* S) → Prop
hP : RespectsIso fun {R S} [CommRing R] [CommRing S] => P
R S : Type u
inst✝¹ : CommRing R
inst✝ : CommRing S
f : R →+* S
s : Set S
hsone : Ideal.span s = ⊤
t : (r : ↑s) → Set (Localization.Away ↑r)
htone : ∀ (r : ↑s), Ideal.span (t r) = ⊤
ht :
  ∀ (r : ↑s),
    ∀ t_1 ∈ t r,
      (fun {R S} [CommRing R] [CommRing S] => P)
        ((algebraMap (Localization.Away ↑r) (Localization.Away t_1)).comp
          ((algebraMap S (Localization.Away ↑r)).comp f))
⊢ ∀ (i : (a : ↑s) × ↑(t a)),
    P
      ((algebraMap S
            ((fun x =>
                match x with
                | ⟨a, b⟩ => Localization.Away ↑b)
              i)).comp
        f)

Proof state:
case h
P : {R S : Type u} → [inst : CommRing R] → [inst_1 : CommRing S] → (R →+* S) → Prop
hP : RespectsIso fun {R S} [CommRing R] [CommRing S] => P
R S : Type u
inst✝¹ : CommRing R
inst✝ : CommRing S
f : R →+* S
s : Set S
hsone : Ideal.span s = ⊤
t : (r : ↑s) → Set (Localization.Away ↑r)
htone : ∀ (r : ↑s), Ideal.span (t r) = ⊤
ht :
  ∀ (r : ↑s),
    ∀ t_1 ∈ t r,
      (fun {R S} [CommRing R] [CommRing S] => P)
        ((algebraMap (Localization.Away ↑r) (Localization.Away t_1)).comp
          ((algebraMap S (Localization.Away ↑r)).comp f))
x✝ : (a : ↑s) × ↑(t a)
a : ↑s
b : ↑(t a)
⊢ Associated (↑b) (↑b * (algebraMap S (Localization.Away ↑a)) (↑a ^ (IsLocalization.Away.sec ↑a ↑b).2))

Tactic:
apply associated_mul_unit_right

Result:
case h.hu
P : {R S : Type u} → [inst : CommRing R] → [inst_1 : CommRing S] → (R →+* S) → Prop
hP : RespectsIso fun {R S} [CommRing R] [CommRing S] => P
R S : Type u
inst✝¹ : CommRing R
inst✝ : CommRing S
f : R →+* S
s : Set S
hsone : Ideal.span s = ⊤
t : (r : ↑s) → Set (Localization.Away ↑r)
htone : ∀ (r : ↑s), Ideal.span (t r) = ⊤
ht :
  ∀ (r : ↑s),
    ∀ t_1 ∈ t r,
      (fun {R S} [CommRing R] [CommRing S] => P)
        ((algebraMap (Localization.Away ↑r) (Localization.Away t_1)).comp
          ((algebraMap S (Localization.Away ↑r)).comp f))
x✝ : (a : ↑s) × ↑(t a)
a : ↑s
b : ↑(t a)
⊢ IsUnit ((algebraMap S (Localization.Away ↑a)) (↑a ^ (IsLocalization.Away.sec ↑a ↑b).2))

Proof state:
case refine_2
P : {R S : Type u} → [inst : CommRing R] → [inst_1 : CommRing S] → (R →+* S) → Prop
hP : RespectsIso fun {R S} [CommRing R] [CommRing S] => P
R S : Type u
inst✝¹ : CommRing R
inst✝ : CommRing S
f : R →+* S
s : Set S
hsone : Ideal.span s = ⊤
t : (r : ↑s) → Set (Localization.Away ↑r)
htone : ∀ (r : ↑s), Ideal.span (t r) = ⊤
ht :
  ∀ (r : ↑s),
    ∀ t_1 ∈ t r,
      (fun {R S} [CommRing R] [CommRing S] => P)
        ((algebraMap (Localization.Away ↑r) (Localization.Away t_1)).comp
          ((algebraMap S (Localization.Away ↑r)).comp f))
a : ↑s
b : ↑(t a)
⊢ P (((algebraMap (Localization.Away ↑a) (Localization.Away ↑b)).comp (algebraMap S (Localization.Away ↑a))).comp f)

Tactic:
apply ht _ _ b.property

Result:
no goals