import CommAlg.krull import Mathlib.RingTheory.Ideal.Operations import Mathlib.RingTheory.FiniteType import Mathlib.Order.Height import Mathlib.RingTheory.PrincipalIdealDomain import Mathlib.RingTheory.DedekindDomain.Basic import Mathlib.RingTheory.Ideal.Quotient import Mathlib.RingTheory.Ideal.MinimalPrime import Mathlib.RingTheory.Localization.AtPrime import Mathlib.AlgebraicGeometry.PrimeSpectrum.Basic import Mathlib.Order.ConditionallyCompleteLattice.Basic namespace Ideal lemma polynomial_over_field_dim_one {K : Type} [Nontrivial K] [Field K] : krullDim (Polynomial K) = 1 := by -- unfold krullDim rw [le_antisymm_iff] constructor · sorry · suffices : ∃I : PrimeSpectrum (Polynomial K), 1 ≤ (height I : WithBot ℕ∞) · obtain ⟨I, h⟩ := this have : (height I : WithBot ℕ∞) ≤ ⨆ (I : PrimeSpectrum (Polynomial K)), ↑(height I) := by apply @le_iSup (WithBot ℕ∞) _ _ _ I exact le_trans h this have primeX : Prime Polynomial.X := @Polynomial.prime_X K _ _ let X := @Polynomial.X K _ have : IsPrime (span {X}) := by refine Iff.mpr (span_singleton_prime ?hp) primeX exact Polynomial.X_ne_zero let P := PrimeSpectrum.mk (span {X}) this unfold height use P have : ⊥ ∈ {J | J < P} := by simp only [Set.mem_setOf_eq] rw [bot_lt_iff_ne_bot] suffices : P.asIdeal ≠ ⊥ · by_contra x rw [PrimeSpectrum.ext_iff] at x contradiction by_contra x simp only [span_singleton_eq_bot] at x have := @Polynomial.X_ne_zero K _ _ contradiction have : {J | J < P}.Nonempty := Set.nonempty_of_mem this rwa [←Set.one_le_chainHeight_iff, ←WithBot.one_le_coe] at this