exfalso
case pos.h₁
M : ℕ
hM : M ≠ 0
f : ArithmeticFunction ℝ
hf : CompletelyMultiplicative f
d : ℕ
hd : Squarefree d
i : (a : (a : ℕ) → a ∈ d.primeFactors → ℕ) → (a ∈ d.primeFactors.pi fun p => Finset.Icc 1 M) → ℕ :=
  fun a x => ∏ p ∈ d.primeFactors.attach, ↑p ^ a ↑p ⋯
a : (a : ℕ) → a ∈ d.primeFactors → ℕ
ha : a ∈ d.primeFactors.pi fun p => Finset.Icc 1 M
p : ℕ
hp : p ∈ d.primeFactors
h : ⟨p, hp⟩ ∉ d.primeFactors.attach
⊢ (↑⟨p, hp⟩ ^ a ↑⟨p, hp⟩ ⋯).factorization p = 0
case pos.h₁
M : ℕ
hM : M ≠ 0
f : ArithmeticFunction ℝ
hf : CompletelyMultiplicative f
d : ℕ
hd : Squarefree d
i : (a : (a : ℕ) → a ∈ d.primeFactors → ℕ) → (a ∈ d.primeFactors.pi fun p => Finset.Icc 1 M) → ℕ :=
  fun a x => ∏ p ∈ d.primeFactors.attach, ↑p ^ a ↑p ⋯
a : (a : ℕ) → a ∈ d.primeFactors → ℕ
ha : a ∈ d.primeFactors.pi fun p => Finset.Icc 1 M
p : ℕ
hp : p ∈ d.primeFactors
h : ⟨p, hp⟩ ∉ d.primeFactors.attach
⊢ False