l3lab/ntp-mathlib huggingface dataset:
theorem WfDvdMonoid.of_exists_prime_factors : WfDvdMonoid α :=
  ⟨by
    classical
      refine'
        RelHomClass.wellFounded
          (RelHom.mk _ _ : (DvdNotUnit : α → α → Prop) →r ((· < ·) : ℕ∞ → ℕ∞ → Prop)) wellFounded_lt
      · intro a
        by_cases h : a = 0
        · exact ⊤
        exact ↑(Multiset.card (Classical.choose (pf a h)))
      rintro a b ⟨ane0, ⟨c, hc, b_eq⟩⟩
      rw [dif_neg ane0]
      by_cases h : b = 0
      · simp [h, lt_top_iff_ne_top]
      · rw [dif_neg h]
        erw [WithTop.coe_lt_coe]
        have cne0 : c ≠ 0 := by
          refine' mt (fun con => _) h
          rw [b_eq, con, mul_zero]
        calc
          Multiset.card (Classical.choose (pf a ane0)) <
              _ + Multiset.card (Classical.choose (pf c cne0)) :=
            lt_add_of_pos_right _
              (Multiset.card_pos.mpr fun con => hc (associated_one_iff_isUnit.mp ?_))
          _ = Multiset.card (Classical.choose (pf a ane0) + Classical.choose (pf c cne0)) :=
            (Multiset.card_add _ _).symm
          _ = Multiset.card (Classical.choose (pf b h)) :=
            Multiset.card_eq_card_of_rel
            (prime_factors_unique ?_ (Classical.choose_spec (pf _ h)).1 ?_)

        · convert (Classical.choose_spec (pf c cne0)).2.symm
          

Proof state:
case h.e'_4
α : Type u_1
inst✝ : CancelCommMonoidWithZero α
pf : ∀ (a : α), a ≠ 0 → ∃ f, (∀ b ∈ f, Prime b) ∧ Multiset.prod f ~ᵤ a
a b : α
ane0 : a ≠ 0
c : α
hc : ¬IsUnit c
b_eq : b = a * c
h : ¬b = 0
cne0 : c ≠ 0
con : Classical.choose (_ : ∃ f, (∀ b ∈ f, Prime b) ∧ Multiset.prod f ~ᵤ c) = 0
⊢ 1 = Multiset.prod (Classical.choose (_ : ∃ f, (∀ b ∈ f, Prime b) ∧ Multiset.prod f ~ᵤ c))

Next tactic:
rw [con, Multiset.prod_zero]
theorem WfDvdMonoid.of_exists_prime_factors : WfDvdMonoid α :=
  ⟨by
    classical
      refine'
        RelHomClass.wellFounded
          (RelHom.mk _ _ : (DvdNotUnit : α → α → Prop) →r ((· < ·) : ℕ∞ → ℕ∞ → Prop)) wellFounded_lt
      · intro a
        by_cases h : a = 0
        · exact ⊤
        exact ↑(Multiset.card (Classical.choose (pf a h)))
      rintro a b ⟨ane0, ⟨c, hc, b_eq⟩⟩
      rw [dif_neg ane0]
      by_cases h : b = 0
      · simp [h, lt_top_iff_ne_top]
      · rw [dif_neg h]
        erw [WithTop.coe_lt_coe]
        have cne0 : c ≠ 0 := by
          refine' mt (fun con => _) h
          rw [b_eq, con, mul_zero]
        calc
          Multiset.card (Classical.choose (pf a ane0)) <
              _ + Multiset.card (Classical.choose (pf c cne0)) :=
            lt_add_of_pos_right _
              (Multiset.card_pos.mpr fun con => hc (associated_one_iff_isUnit.mp ?_))
          _ = Multiset.card (Classical.choose (pf a ane0) + Classical.choose (pf c cne0)) :=
            (Multiset.card_add _ _).symm
          _ = Multiset.card (Classical.choose (pf b h)) :=
            Multiset.card_eq_card_of_rel
            (prime_factors_unique ?_ (Classical.choose_spec (pf _ h)).1 ?_)

        · convert (Classical.choose_spec (pf c cne0)).2.symm
          rw [con, Multiset.prod_zero]
        · 

Proof state:
case neg.calc_2
α : Type u_1
inst✝ : CancelCommMonoidWithZero α
pf : ∀ (a : α), a ≠ 0 → ∃ f, (∀ b ∈ f, Prime b) ∧ Multiset.prod f ~ᵤ a
a b : α
ane0 : a ≠ 0
c : α
hc : ¬IsUnit c
b_eq : b = a * c
h : ¬b = 0
cne0 : c ≠ 0
⊢ ∀
    x ∈
      Classical.choose (_ : ∃ f, (∀ b ∈ f, Prime b) ∧ Multiset.prod f ~ᵤ a) +
        Classical.choose (_ : ∃ f, (∀ b ∈ f, Prime b) ∧ Multiset.prod f ~ᵤ c),
    Prime x

Next tactic:
intro x hadd
theorem WfDvdMonoid.of_exists_prime_factors : WfDvdMonoid α :=
  ⟨by
    classical
      refine'
        RelHomClass.wellFounded
          (RelHom.mk _ _ : (DvdNotUnit : α → α → Prop) →r ((· < ·) : ℕ∞ → ℕ∞ → Prop)) wellFounded_lt
      · intro a
        by_cases h : a = 0
        · exact ⊤
        exact ↑(Multiset.card (Classical.choose (pf a h)))
      rintro a b ⟨ane0, ⟨c, hc, b_eq⟩⟩
      rw [dif_neg ane0]
      by_cases h : b = 0
      · simp [h, lt_top_iff_ne_top]
      · rw [dif_neg h]
        erw [WithTop.coe_lt_coe]
        have cne0 : c ≠ 0 := by
          refine' mt (fun con => _) h
          rw [b_eq, con, mul_zero]
        calc
          Multiset.card (Classical.choose (pf a ane0)) <
              _ + Multiset.card (Classical.choose (pf c cne0)) :=
            lt_add_of_pos_right _
              (Multiset.card_pos.mpr fun con => hc (associated_one_iff_isUnit.mp ?_))
          _ = Multiset.card (Classical.choose (pf a ane0) + Classical.choose (pf c cne0)) :=
            (Multiset.card_add _ _).symm
          _ = Multiset.card (Classical.choose (pf b h)) :=
            Multiset.card_eq_card_of_rel
            (prime_factors_unique ?_ (Classical.choose_spec (pf _ h)).1 ?_)

        · convert (Classical.choose_spec (pf c cne0)).2.symm
          rw [con, Multiset.prod_zero]
        · intro x hadd
          

Proof state:
case neg.calc_2
α : Type u_1
inst✝ : CancelCommMonoidWithZero α
pf : ∀ (a : α), a ≠ 0 → ∃ f, (∀ b ∈ f, Prime b) ∧ Multiset.prod f ~ᵤ a
a b : α
ane0 : a ≠ 0
c : α
hc : ¬IsUnit c
b_eq : b = a * c
h : ¬b = 0
cne0 : c ≠ 0
x : α
hadd :
  x ∈
    Classical.choose (_ : ∃ f, (∀ b ∈ f, Prime b) ∧ Multiset.prod f ~ᵤ a) +
      Classical.choose (_ : ∃ f, (∀ b ∈ f, Prime b) ∧ Multiset.prod f ~ᵤ c)
⊢ Prime x

Next tactic:
rw [Multiset.mem_add] at hadd
theorem WfDvdMonoid.of_exists_prime_factors : WfDvdMonoid α :=
  ⟨by
    classical
      refine'
        RelHomClass.wellFounded
          (RelHom.mk _ _ : (DvdNotUnit : α → α → Prop) →r ((· < ·) : ℕ∞ → ℕ∞ → Prop)) wellFounded_lt
      · intro a
        by_cases h : a = 0
        · exact ⊤
        exact ↑(Multiset.card (Classical.choose (pf a h)))
      rintro a b ⟨ane0, ⟨c, hc, b_eq⟩⟩
      rw [dif_neg ane0]
      by_cases h : b = 0
      · simp [h, lt_top_iff_ne_top]
      · rw [dif_neg h]
        erw [WithTop.coe_lt_coe]
        have cne0 : c ≠ 0 := by
          refine' mt (fun con => _) h
          rw [b_eq, con, mul_zero]
        calc
          Multiset.card (Classical.choose (pf a ane0)) <
              _ + Multiset.card (Classical.choose (pf c cne0)) :=
            lt_add_of_pos_right _
              (Multiset.card_pos.mpr fun con => hc (associated_one_iff_isUnit.mp ?_))
          _ = Multiset.card (Classical.choose (pf a ane0) + Classical.choose (pf c cne0)) :=
            (Multiset.card_add _ _).symm
          _ = Multiset.card (Classical.choose (pf b h)) :=
            Multiset.card_eq_card_of_rel
            (prime_factors_unique ?_ (Classical.choose_spec (pf _ h)).1 ?_)

        · convert (Classical.choose_spec (pf c cne0)).2.symm
          rw [con, Multiset.prod_zero]
        · intro x hadd
          rw [Multiset.mem_add] at hadd
          

Proof state:
case neg.calc_2
α : Type u_1
inst✝ : CancelCommMonoidWithZero α
pf : ∀ (a : α), a ≠ 0 → ∃ f, (∀ b ∈ f, Prime b) ∧ Multiset.prod f ~ᵤ a
a b : α
ane0 : a ≠ 0
c : α
hc : ¬IsUnit c
b_eq : b = a * c
h : ¬b = 0
cne0 : c ≠ 0
x : α
hadd :
  x ∈ Classical.choose (_ : ∃ f, (∀ b ∈ f, Prime b) ∧ Multiset.prod f ~ᵤ a) ∨
    x ∈ Classical.choose (_ : ∃ f, (∀ b ∈ f, Prime b) ∧ Multiset.prod f ~ᵤ c)
⊢ Prime x

Next tactic:
cases' hadd with h h
theorem WfDvdMonoid.of_exists_prime_factors : WfDvdMonoid α :=
  ⟨by
    classical
      refine'
        RelHomClass.wellFounded
          (RelHom.mk _ _ : (DvdNotUnit : α → α → Prop) →r ((· < ·) : ℕ∞ → ℕ∞ → Prop)) wellFounded_lt
      · intro a
        by_cases h : a = 0
        · exact ⊤
        exact ↑(Multiset.card (Classical.choose (pf a h)))
      rintro a b ⟨ane0, ⟨c, hc, b_eq⟩⟩
      rw [dif_neg ane0]
      by_cases h : b = 0
      · simp [h, lt_top_iff_ne_top]
      · rw [dif_neg h]
        erw [WithTop.coe_lt_coe]
        have cne0 : c ≠ 0 := by
          refine' mt (fun con => _) h
          rw [b_eq, con, mul_zero]
        calc
          Multiset.card (Classical.choose (pf a ane0)) <
              _ + Multiset.card (Classical.choose (pf c cne0)) :=
            lt_add_of_pos_right _
              (Multiset.card_pos.mpr fun con => hc (associated_one_iff_isUnit.mp ?_))
          _ = Multiset.card (Classical.choose (pf a ane0) + Classical.choose (pf c cne0)) :=
            (Multiset.card_add _ _).symm
          _ = Multiset.card (Classical.choose (pf b h)) :=
            Multiset.card_eq_card_of_rel
            (prime_factors_unique ?_ (Classical.choose_spec (pf _ h)).1 ?_)

        · convert (Classical.choose_spec (pf c cne0)).2.symm
          rw [con, Multiset.prod_zero]
        · intro x hadd
          rw [Multiset.mem_add] at hadd
          cases' hadd with h h <;> 

Proof state:
case neg.calc_2.inl
α : Type u_1
inst✝ : CancelCommMonoidWithZero α
pf : ∀ (a : α), a ≠ 0 → ∃ f, (∀ b ∈ f, Prime b) ∧ Multiset.prod f ~ᵤ a
a b : α
ane0 : a ≠ 0
c : α
hc : ¬IsUnit c
b_eq : b = a * c
h✝ : ¬b = 0
cne0 : c ≠ 0
x : α
h : x ∈ Classical.choose (_ : ∃ f, (∀ b ∈ f, Prime b) ∧ Multiset.prod f ~ᵤ a)
⊢ Prime x

Next tactic:
apply (Classical.choose_spec (pf _ _)).1 _ h
theorem WfDvdMonoid.of_exists_prime_factors : WfDvdMonoid α :=
  ⟨by
    classical
      refine'
        RelHomClass.wellFounded
          (RelHom.mk _ _ : (DvdNotUnit : α → α → Prop) →r ((· < ·) : ℕ∞ → ℕ∞ → Prop)) wellFounded_lt
      · intro a
        by_cases h : a = 0
        · exact ⊤
        exact ↑(Multiset.card (Classical.choose (pf a h)))
      rintro a b ⟨ane0, ⟨c, hc, b_eq⟩⟩
      rw [dif_neg ane0]
      by_cases h : b = 0
      · simp [h, lt_top_iff_ne_top]
      · rw [dif_neg h]
        erw [WithTop.coe_lt_coe]
        have cne0 : c ≠ 0 := by
          refine' mt (fun con => _) h
          rw [b_eq, con, mul_zero]
        calc
          Multiset.card (Classical.choose (pf a ane0)) <
              _ + Multiset.card (Classical.choose (pf c cne0)) :=
            lt_add_of_pos_right _
              (Multiset.card_pos.mpr fun con => hc (associated_one_iff_isUnit.mp ?_))
          _ = Multiset.card (Classical.choose (pf a ane0) + Classical.choose (pf c cne0)) :=
            (Multiset.card_add _ _).symm
          _ = Multiset.card (Classical.choose (pf b h)) :=
            Multiset.card_eq_card_of_rel
            (prime_factors_unique ?_ (Classical.choose_spec (pf _ h)).1 ?_)

        · convert (Classical.choose_spec (pf c cne0)).2.symm
          rw [con, Multiset.prod_zero]
        · intro x hadd
          rw [Multiset.mem_add] at hadd
          cases' hadd with h h <;> 

Proof state:
case neg.calc_2.inr
α : Type u_1
inst✝ : CancelCommMonoidWithZero α
pf : ∀ (a : α), a ≠ 0 → ∃ f, (∀ b ∈ f, Prime b) ∧ Multiset.prod f ~ᵤ a
a b : α
ane0 : a ≠ 0
c : α
hc : ¬IsUnit c
b_eq : b = a * c
h✝ : ¬b = 0
cne0 : c ≠ 0
x : α
h : x ∈ Classical.choose (_ : ∃ f, (∀ b ∈ f, Prime b) ∧ Multiset.prod f ~ᵤ c)
⊢ Prime x

Next tactic:
apply (Classical.choose_spec (pf _ _)).1 _ h
theorem WfDvdMonoid.of_exists_prime_factors : WfDvdMonoid α :=
  ⟨by
    classical
      refine'
        RelHomClass.wellFounded
          (RelHom.mk _ _ : (DvdNotUnit : α → α → Prop) →r ((· < ·) : ℕ∞ → ℕ∞ → Prop)) wellFounded_lt
      · intro a
        by_cases h : a = 0
        · exact ⊤
        exact ↑(Multiset.card (Classical.choose (pf a h)))
      rintro a b ⟨ane0, ⟨c, hc, b_eq⟩⟩
      rw [dif_neg ane0]
      by_cases h : b = 0
      · simp [h, lt_top_iff_ne_top]
      · rw [dif_neg h]
        erw [WithTop.coe_lt_coe]
        have cne0 : c ≠ 0 := by
          refine' mt (fun con => _) h
          rw [b_eq, con, mul_zero]
        calc
          Multiset.card (Classical.choose (pf a ane0)) <
              _ + Multiset.card (Classical.choose (pf c cne0)) :=
            lt_add_of_pos_right _
              (Multiset.card_pos.mpr fun con => hc (associated_one_iff_isUnit.mp ?_))
          _ = Multiset.card (Classical.choose (pf a ane0) + Classical.choose (pf c cne0)) :=
            (Multiset.card_add _ _).symm
          _ = Multiset.card (Classical.choose (pf b h)) :=
            Multiset.card_eq_card_of_rel
            (prime_factors_unique ?_ (Classical.choose_spec (pf _ h)).1 ?_)

        · convert (Classical.choose_spec (pf c cne0)).2.symm
          rw [con, Multiset.prod_zero]
        · intro x hadd
          rw [Multiset.mem_add] at hadd
          cases' hadd with h h <;> apply (Classical.choose_spec (pf _ _)).1 _ h <;> 

Proof state:
α : Type u_1
inst✝ : CancelCommMonoidWithZero α
pf : ∀ (a : α), a ≠ 0 → ∃ f, (∀ b ∈ f, Prime b) ∧ Multiset.prod f ~ᵤ a
a b : α
ane0 : a ≠ 0
c : α
hc : ¬IsUnit c
b_eq : b = a * c
h✝ : ¬b = 0
cne0 : c ≠ 0
x : α
h : x ∈ Classical.choose (_ : ∃ f, (∀ b ∈ f, Prime b) ∧ Multiset.prod f ~ᵤ a)
⊢ a ≠ 0

Next tactic:
assumption
theorem WfDvdMonoid.of_exists_prime_factors : WfDvdMonoid α :=
  ⟨by
    classical
      refine'
        RelHomClass.wellFounded
          (RelHom.mk _ _ : (DvdNotUnit : α → α → Prop) →r ((· < ·) : ℕ∞ → ℕ∞ → Prop)) wellFounded_lt
      · intro a
        by_cases h : a = 0
        · exact ⊤
        exact ↑(Multiset.card (Classical.choose (pf a h)))
      rintro a b ⟨ane0, ⟨c, hc, b_eq⟩⟩
      rw [dif_neg ane0]
      by_cases h : b = 0
      · simp [h, lt_top_iff_ne_top]
      · rw [dif_neg h]
        erw [WithTop.coe_lt_coe]
        have cne0 : c ≠ 0 := by
          refine' mt (fun con => _) h
          rw [b_eq, con, mul_zero]
        calc
          Multiset.card (Classical.choose (pf a ane0)) <
              _ + Multiset.card (Classical.choose (pf c cne0)) :=
            lt_add_of_pos_right _
              (Multiset.card_pos.mpr fun con => hc (associated_one_iff_isUnit.mp ?_))
          _ = Multiset.card (Classical.choose (pf a ane0) + Classical.choose (pf c cne0)) :=
            (Multiset.card_add _ _).symm
          _ = Multiset.card (Classical.choose (pf b h)) :=
            Multiset.card_eq_card_of_rel
            (prime_factors_unique ?_ (Classical.choose_spec (pf _ h)).1 ?_)

        · convert (Classical.choose_spec (pf c cne0)).2.symm
          rw [con, Multiset.prod_zero]
        · intro x hadd
          rw [Multiset.mem_add] at hadd
          cases' hadd with h h <;> apply (Classical.choose_spec (pf _ _)).1 _ h <;> 

Proof state:
α : Type u_1
inst✝ : CancelCommMonoidWithZero α
pf : ∀ (a : α), a ≠ 0 → ∃ f, (∀ b ∈ f, Prime b) ∧ Multiset.prod f ~ᵤ a
a b : α
ane0 : a ≠ 0
c : α
hc : ¬IsUnit c
b_eq : b = a * c
h✝ : ¬b = 0
cne0 : c ≠ 0
x : α
h : x ∈ Classical.choose (_ : ∃ f, (∀ b ∈ f, Prime b) ∧ Multiset.prod f ~ᵤ c)
⊢ c ≠ 0

Next tactic:
assumption
theorem WfDvdMonoid.of_exists_prime_factors : WfDvdMonoid α :=
  ⟨by
    classical
      refine'
        RelHomClass.wellFounded
          (RelHom.mk _ _ : (DvdNotUnit : α → α → Prop) →r ((· < ·) : ℕ∞ → ℕ∞ → Prop)) wellFounded_lt
      · intro a
        by_cases h : a = 0
        · exact ⊤
        exact ↑(Multiset.card (Classical.choose (pf a h)))
      rintro a b ⟨ane0, ⟨c, hc, b_eq⟩⟩
      rw [dif_neg ane0]
      by_cases h : b = 0
      · simp [h, lt_top_iff_ne_top]
      · rw [dif_neg h]
        erw [WithTop.coe_lt_coe]
        have cne0 : c ≠ 0 := by
          refine' mt (fun con => _) h
          rw [b_eq, con, mul_zero]
        calc
          Multiset.card (Classical.choose (pf a ane0)) <
              _ + Multiset.card (Classical.choose (pf c cne0)) :=
            lt_add_of_pos_right _
              (Multiset.card_pos.mpr fun con => hc (associated_one_iff_isUnit.mp ?_))
          _ = Multiset.card (Classical.choose (pf a ane0) + Classical.choose (pf c cne0)) :=
            (Multiset.card_add _ _).symm
          _ = Multiset.card (Classical.choose (pf b h)) :=
            Multiset.card_eq_card_of_rel
            (prime_factors_unique ?_ (Classical.choose_spec (pf _ h)).1 ?_)

        · convert (Classical.choose_spec (pf c cne0)).2.symm
          rw [con, Multiset.prod_zero]
        · intro x hadd
          rw [Multiset.mem_add] at hadd
          cases' hadd with h h <;> apply (Classical.choose_spec (pf _ _)).1 _ h <;> assumption
        · 

Proof state:
case neg.calc_3
α : Type u_1
inst✝ : CancelCommMonoidWithZero α
pf : ∀ (a : α), a ≠ 0 → ∃ f, (∀ b ∈ f, Prime b) ∧ Multiset.prod f ~ᵤ a
a b : α
ane0 : a ≠ 0
c : α
hc : ¬IsUnit c
b_eq : b = a * c
h : ¬b = 0
cne0 : c ≠ 0
⊢ Multiset.prod
      (Classical.choose (_ : ∃ f, (∀ b ∈ f, Prime b) ∧ Multiset.prod f ~ᵤ a) +
        Classical.choose (_ : ∃ f, (∀ b ∈ f, Prime b) ∧ Multiset.prod f ~ᵤ c)) ~ᵤ
    Multiset.prod (Classical.choose (_ : ∃ f, (∀ b ∈ f, Prime b) ∧ Multiset.prod f ~ᵤ b))

Next tactic:
rw [Multiset.prod_add]
theorem WfDvdMonoid.of_exists_prime_factors : WfDvdMonoid α :=
  ⟨by
    classical
      refine'
        RelHomClass.wellFounded
          (RelHom.mk _ _ : (DvdNotUnit : α → α → Prop) →r ((· < ·) : ℕ∞ → ℕ∞ → Prop)) wellFounded_lt
      · intro a
        by_cases h : a = 0
        · exact ⊤
        exact ↑(Multiset.card (Classical.choose (pf a h)))
      rintro a b ⟨ane0, ⟨c, hc, b_eq⟩⟩
      rw [dif_neg ane0]
      by_cases h : b = 0
      · simp [h, lt_top_iff_ne_top]
      · rw [dif_neg h]
        erw [WithTop.coe_lt_coe]
        have cne0 : c ≠ 0 := by
          refine' mt (fun con => _) h
          rw [b_eq, con, mul_zero]
        calc
          Multiset.card (Classical.choose (pf a ane0)) <
              _ + Multiset.card (Classical.choose (pf c cne0)) :=
            lt_add_of_pos_right _
              (Multiset.card_pos.mpr fun con => hc (associated_one_iff_isUnit.mp ?_))
          _ = Multiset.card (Classical.choose (pf a ane0) + Classical.choose (pf c cne0)) :=
            (Multiset.card_add _ _).symm
          _ = Multiset.card (Classical.choose (pf b h)) :=
            Multiset.card_eq_card_of_rel
            (prime_factors_unique ?_ (Classical.choose_spec (pf _ h)).1 ?_)

        · convert (Classical.choose_spec (pf c cne0)).2.symm
          rw [con, Multiset.prod_zero]
        · intro x hadd
          rw [Multiset.mem_add] at hadd
          cases' hadd with h h <;> apply (Classical.choose_spec (pf _ _)).1 _ h <;> assumption
        · rw [Multiset.prod_add]
          

Proof state:
case neg.calc_3
α : Type u_1
inst✝ : CancelCommMonoidWithZero α
pf : ∀ (a : α), a ≠ 0 → ∃ f, (∀ b ∈ f, Prime b) ∧ Multiset.prod f ~ᵤ a
a b : α
ane0 : a ≠ 0
c : α
hc : ¬IsUnit c
b_eq : b = a * c
h : ¬b = 0
cne0 : c ≠ 0
⊢ Multiset.prod (Classical.choose (_ : ∃ f, (∀ b ∈ f, Prime b) ∧ Multiset.prod f ~ᵤ a)) *
      Multiset.prod (Classical.choose (_ : ∃ f, (∀ b ∈ f, Prime b) ∧ Multiset.prod f ~ᵤ c)) ~ᵤ
    Multiset.prod (Classical.choose (_ : ∃ f, (∀ b ∈ f, Prime b) ∧ Multiset.prod f ~ᵤ b))

Next tactic:
trans a * c
theorem WfDvdMonoid.of_exists_prime_factors : WfDvdMonoid α :=
  ⟨by
    classical
      refine'
        RelHomClass.wellFounded
          (RelHom.mk _ _ : (DvdNotUnit : α → α → Prop) →r ((· < ·) : ℕ∞ → ℕ∞ → Prop)) wellFounded_lt
      · intro a
        by_cases h : a = 0
        · exact ⊤
        exact ↑(Multiset.card (Classical.choose (pf a h)))
      rintro a b ⟨ane0, ⟨c, hc, b_eq⟩⟩
      rw [dif_neg ane0]
      by_cases h : b = 0
      · simp [h, lt_top_iff_ne_top]
      · rw [dif_neg h]
        erw [WithTop.coe_lt_coe]
        have cne0 : c ≠ 0 := by
          refine' mt (fun con => _) h
          rw [b_eq, con, mul_zero]
        calc
          Multiset.card (Classical.choose (pf a ane0)) <
              _ + Multiset.card (Classical.choose (pf c cne0)) :=
            lt_add_of_pos_right _
              (Multiset.card_pos.mpr fun con => hc (associated_one_iff_isUnit.mp ?_))
          _ = Multiset.card (Classical.choose (pf a ane0) + Classical.choose (pf c cne0)) :=
            (Multiset.card_add _ _).symm
          _ = Multiset.card (Classical.choose (pf b h)) :=
            Multiset.card_eq_card_of_rel
            (prime_factors_unique ?_ (Classical.choose_spec (pf _ h)).1 ?_)

        · convert (Classical.choose_spec (pf c cne0)).2.symm
          rw [con, Multiset.prod_zero]
        · intro x hadd
          rw [Multiset.mem_add] at hadd
          cases' hadd with h h <;> apply (Classical.choose_spec (pf _ _)).1 _ h <;> assumption
        · rw [Multiset.prod_add]
          trans a * c
          · 

Proof state:
α : Type u_1
inst✝ : CancelCommMonoidWithZero α
pf : ∀ (a : α), a ≠ 0 → ∃ f, (∀ b ∈ f, Prime b) ∧ Multiset.prod f ~ᵤ a
a b : α
ane0 : a ≠ 0
c : α
hc : ¬IsUnit c
b_eq : b = a * c
h : ¬b = 0
cne0 : c ≠ 0
⊢ Multiset.prod (Classical.choose (_ : ∃ f, (∀ b ∈ f, Prime b) ∧ Multiset.prod f ~ᵤ a)) *
      Multiset.prod (Classical.choose (_ : ∃ f, (∀ b ∈ f, Prime b) ∧ Multiset.prod f ~ᵤ c)) ~ᵤ
    a * c

Next tactic:
apply Associated.mul_mul
theorem WfDvdMonoid.of_exists_prime_factors : WfDvdMonoid α :=
  ⟨by
    classical
      refine'
        RelHomClass.wellFounded
          (RelHom.mk _ _ : (DvdNotUnit : α → α → Prop) →r ((· < ·) : ℕ∞ → ℕ∞ → Prop)) wellFounded_lt
      · intro a
        by_cases h : a = 0
        · exact ⊤
        exact ↑(Multiset.card (Classical.choose (pf a h)))
      rintro a b ⟨ane0, ⟨c, hc, b_eq⟩⟩
      rw [dif_neg ane0]
      by_cases h : b = 0
      · simp [h, lt_top_iff_ne_top]
      · rw [dif_neg h]
        erw [WithTop.coe_lt_coe]
        have cne0 : c ≠ 0 := by
          refine' mt (fun con => _) h
          rw [b_eq, con, mul_zero]
        calc
          Multiset.card (Classical.choose (pf a ane0)) <
              _ + Multiset.card (Classical.choose (pf c cne0)) :=
            lt_add_of_pos_right _
              (Multiset.card_pos.mpr fun con => hc (associated_one_iff_isUnit.mp ?_))
          _ = Multiset.card (Classical.choose (pf a ane0) + Classical.choose (pf c cne0)) :=
            (Multiset.card_add _ _).symm
          _ = Multiset.card (Classical.choose (pf b h)) :=
            Multiset.card_eq_card_of_rel
            (prime_factors_unique ?_ (Classical.choose_spec (pf _ h)).1 ?_)

        · convert (Classical.choose_spec (pf c cne0)).2.symm
          rw [con, Multiset.prod_zero]
        · intro x hadd
          rw [Multiset.mem_add] at hadd
          cases' hadd with h h <;> apply (Classical.choose_spec (pf _ _)).1 _ h <;> assumption
        · rw [Multiset.prod_add]
          trans a * c
          · apply Associated.mul_mul <;> 

Proof state:
case a
α : Type u_1
inst✝ : CancelCommMonoidWithZero α
pf : ∀ (a : α), a ≠ 0 → ∃ f, (∀ b ∈ f, Prime b) ∧ Multiset.prod f ~ᵤ a
a b : α
ane0 : a ≠ 0
c : α
hc : ¬IsUnit c
b_eq : b = a * c
h : ¬b = 0
cne0 : c ≠ 0
⊢ Multiset.prod (Classical.choose (_ : ∃ f, (∀ b ∈ f, Prime b) ∧ Multiset.prod f ~ᵤ a)) ~ᵤ a

Next tactic:
apply (Classical.choose_spec (pf _ _)).2
theorem WfDvdMonoid.of_exists_prime_factors : WfDvdMonoid α :=
  ⟨by
    classical
      refine'
        RelHomClass.wellFounded
          (RelHom.mk _ _ : (DvdNotUnit : α → α → Prop) →r ((· < ·) : ℕ∞ → ℕ∞ → Prop)) wellFounded_lt
      · intro a
        by_cases h : a = 0
        · exact ⊤
        exact ↑(Multiset.card (Classical.choose (pf a h)))
      rintro a b ⟨ane0, ⟨c, hc, b_eq⟩⟩
      rw [dif_neg ane0]
      by_cases h : b = 0
      · simp [h, lt_top_iff_ne_top]
      · rw [dif_neg h]
        erw [WithTop.coe_lt_coe]
        have cne0 : c ≠ 0 := by
          refine' mt (fun con => _) h
          rw [b_eq, con, mul_zero]
        calc
          Multiset.card (Classical.choose (pf a ane0)) <
              _ + Multiset.card (Classical.choose (pf c cne0)) :=
            lt_add_of_pos_right _
              (Multiset.card_pos.mpr fun con => hc (associated_one_iff_isUnit.mp ?_))
          _ = Multiset.card (Classical.choose (pf a ane0) + Classical.choose (pf c cne0)) :=
            (Multiset.card_add _ _).symm
          _ = Multiset.card (Classical.choose (pf b h)) :=
            Multiset.card_eq_card_of_rel
            (prime_factors_unique ?_ (Classical.choose_spec (pf _ h)).1 ?_)

        · convert (Classical.choose_spec (pf c cne0)).2.symm
          rw [con, Multiset.prod_zero]
        · intro x hadd
          rw [Multiset.mem_add] at hadd
          cases' hadd with h h <;> apply (Classical.choose_spec (pf _ _)).1 _ h <;> assumption
        · rw [Multiset.prod_add]
          trans a * c
          · apply Associated.mul_mul <;> 

Proof state:
case a
α : Type u_1
inst✝ : CancelCommMonoidWithZero α
pf : ∀ (a : α), a ≠ 0 → ∃ f, (∀ b ∈ f, Prime b) ∧ Multiset.prod f ~ᵤ a
a b : α
ane0 : a ≠ 0
c : α
hc : ¬IsUnit c
b_eq : b = a * c
h : ¬b = 0
cne0 : c ≠ 0
⊢ Multiset.prod (Classical.choose (_ : ∃ f, (∀ b ∈ f, Prime b) ∧ Multiset.prod f ~ᵤ c)) ~ᵤ c

Next tactic:
apply (Classical.choose_spec (pf _ _)).2