feat(RingTheory): lemmas for minimal primes to lessen defeq abuse

Mathlib/RingTheory/Ideal/AssociatedPrime/Localization.lean

@@ -131,10 +131,11 @@ variable (R M) in
 lemma minimalPrimes_annihilator_subset_associatedPrimes [IsNoetherianRing R] [Module.Finite R M] :
     (Module.annihilator R M).minimalPrimes ⊆ associatedPrimes R M := by
   intro p hp
-  have prime := hp.1.1
+  have prime := Ideal.minimalPrimes_isPrime hp
   let Rₚ := Localization.AtPrime p
   have : Nontrivial (LocalizedModule p.primeCompl M) := by
-    simpa [← Module.mem_support_iff (p := ⟨p, prime⟩), Module.support_eq_zeroLocus] using hp.1.2
+    simpa [← Module.mem_support_iff (p := ⟨p, prime⟩), Module.support_eq_zeroLocus] using
+      Ideal.le_minimalPrimes hp
   rcases associatedPrimes.nonempty Rₚ (LocalizedModule p.primeCompl M) with ⟨q, hq⟩
   have q_prime : q.IsPrime := IsAssociatedPrime.isPrime hq
   simp only [← preimage_comap_associatedPrimes_eq_associatedPrimes_of_isLocalizedModule p.primeCompl

Mathlib/RingTheory/Ideal/Height.lean

@@ -117,7 +117,7 @@ theorem Ideal.height_mono {I J : Ideal R} (h : I ≤ J) : I.height ≤ J.height
   simp only [height]
   refine le_iInf₂ (fun p hp ↦ ?_)
   have := Ideal.minimalPrimes_isPrime hp
-  obtain ⟨q, hq, e⟩ := Ideal.exists_minimalPrimes_le (h.trans hp.1.2)
+  obtain ⟨q, hq, e⟩ := Ideal.exists_minimalPrimes_le (h.trans (Ideal.le_minimalPrimes hp))
   haveI := Ideal.minimalPrimes_isPrime hq
   exact (iInf₂_le q hq).trans (Ideal.primeHeight_mono e)
 
@@ -130,8 +130,8 @@ lemma Ideal.height_strict_mono_of_is_prime {I J : Ideal R} [I.IsPrime]
     exact I.primeHeight_lt_top
   · rw [← ENat.add_one_le_iff I.primeHeight_ne_top, Ideal.height]
     refine le_iInf₂ (fun K hK ↦ ?_)
-    haveI := Ideal.minimalPrimes_isPrime hK
-    have : I < K := lt_of_lt_of_le h hK.1.2
+    have := Ideal.minimalPrimes_isPrime hK
+    have : I < K := lt_of_lt_of_le h (Ideal.le_minimalPrimes hK)
     exact Ideal.primeHeight_add_one_le_of_lt this
 
 lemma Ideal.primeHeight_le_ringKrullDim {I : Ideal R} [I.IsPrime] :
@@ -179,10 +179,10 @@ lemma Ideal.mem_minimalPrimes_of_height_eq {I J : Ideal R} (e : I ≤ J) [J.IsPr
   obtain ⟨p, h₁, h₂⟩ := Ideal.exists_minimalPrimes_le e
   convert h₁
   refine (eq_of_le_of_not_lt h₂ fun h₃ ↦ ?_).symm
-  have := h₁.1.1
+  have := Ideal.minimalPrimes_isPrime h₁
   have := finiteHeight_of_le h₂ IsPrime.ne_top'
-  exact lt_irrefl _
-     ((height_strict_mono_of_is_prime h₃).trans_le (e'.trans <| height_mono h₁.1.2))
+  exact lt_irrefl _ ((height_strict_mono_of_is_prime h₃).trans_le
+    (e'.trans <| height_mono (Ideal.le_minimalPrimes h₁)))
 
 /-- A prime ideal has height zero if and only if it is minimal -/
 lemma Ideal.primeHeight_eq_zero_iff {I : Ideal R} [I.IsPrime] :
@@ -201,7 +201,9 @@ lemma Ideal.primeHeight_eq_zero_iff {I : Ideal R} [I.IsPrime] :
 lemma Ideal.height_bot [Nontrivial R] : (⊥ : Ideal R).height = 0 := by
   obtain ⟨p, hp⟩ := Ideal.nonempty_minimalPrimes (R := R) (I := ⊥) top_ne_bot.symm
   simp only [Ideal.height, ENat.iInf_eq_zero]
-  exact ⟨p, hp, haveI := hp.1.1; primeHeight_eq_zero_iff.mpr hp⟩
+  refine ⟨p, hp, ?_⟩
+  have := Ideal.minimalPrimes_isPrime hp
+  rw [primeHeight_eq_zero_iff.mpr hp]
 
 /-- In a trivial commutative ring, the height of any ideal is `∞`. -/
 @[simp, nontriviality]
@@ -281,7 +283,7 @@ lemma RingEquiv.height_comap {S : Type*} [CommRing S] (e : R ≃+* S) (I : Ideal
     rw [← Ideal.comap_coe,
       Ideal.comap_minimalPrimes_eq_of_surjective (f := (↑e : R →+* S)) e.surjective]
     exact e.idealComapOrderIso.injective.mem_set_image.symm
-  · have : J.IsPrime := h.1.1
+  · have : J.IsPrime := Ideal.minimalPrimes_isPrime h
     simp only [EquivLike.coe_coe, RingEquiv.idealComapOrderIso_apply,
       ← Ideal.height_eq_primeHeight, RingEquiv.height_comap_of_isPrime]
 
@@ -375,7 +377,7 @@ lemma exists_spanRank_le_and_le_height_of_le_height [IsNoetherianRing R] (I : Id
       refine (Ideal.subset_union_prime ⊥ ⊥ ?_).not.mpr ?_
       · rintro K hK - -
         rw [Set.Finite.mem_toFinset] at hK
-        exact hK.1.1.1
+        exact Ideal.minimalPrimes_isPrime hK.1
       · push Not
         intro K hK e
         have := hr.trans (Ideal.height_mono e)
@@ -391,7 +393,7 @@ lemma exists_spanRank_le_and_le_height_of_le_height [IsNoetherianRing R] (I : Id
       push_cast
       exact add_le_add h₂ ((Submodule.spanRank_span_le_card _).trans (by simp))
     · refine le_iInf₂ (fun p hp ↦ ?_)
-      have := hp.1.1
+      have := Ideal.minimalPrimes_isPrime hp
       by_cases h : p.height = ⊤
       · rw [← p.height_eq_primeHeight, h]
         exact le_top
@@ -408,9 +410,10 @@ lemma exists_spanRank_le_and_le_height_of_le_height [IsNoetherianRing R] (I : Id
           apply le_antisymm
           · rwa [← p.height_eq_primeHeight]
           · rwa [← e]
-        refine ⟨mem_minimalPrimes_of_primeHeight_eq_height (le_sup_left.trans hp.1.2) this.symm, ?_⟩
+        refine ⟨mem_minimalPrimes_of_primeHeight_eq_height
+          (le_sup_left.trans (Ideal.le_minimalPrimes hp)) this.symm, ?_⟩
         rwa [p.height_eq_primeHeight, eq_comm]
-      · exact hp.1.2 <| Ideal.mem_sup_right <| Ideal.subset_span <| Set.mem_singleton x
+      · exact (Ideal.le_minimalPrimes hp) <| Ideal.mem_sup_right <| mem_span_singleton_self x
 
 /-- In a nontrivial commutative ring `R`, the supremum of heights of all ideals is equal to the
 Krull dimension of `R`. -/

Mathlib/RingTheory/Ideal/KrullsHeightTheorem.lean

@@ -83,7 +83,7 @@ lemma Ideal.height_le_one_of_isPrincipal_of_mem_minimalPrimes_of_isLocalRing
     ← (IsLocalization.orderEmbedding q.primeCompl (Localization.AtPrime q)).map_rel_iff]
   refine Submodule.le_of_le_smul_of_le_jacobson_bot (I := I) (IsNoetherian.noetherian _) ?_ ?_
   · rw [IsLocalRing.jacobson_eq_maximalIdeal]
-    exacts [hp.1.2, bot_ne_top]
+    exacts [Ideal.le_minimalPrimes hp, bot_ne_top]
   · replace hn := congr(Ideal.comap (Ideal.Quotient.mk I) $(hn _ n.le_succ))
     simp only [qs, OrderHom.coe_mk, ← RingHom.ker_eq_comap_bot, Ideal.mk_ker,
       Ideal.comap_map_of_surjective _ Ideal.Quotient.mk_surjective] at hn
@@ -106,7 +106,7 @@ lemma Ideal.height_le_one_of_isPrincipal_of_mem_minimalPrimes_of_isLocalRing
   has height at most 1. -/
 lemma Ideal.height_le_one_of_isPrincipal_of_mem_minimalPrimes
     (I : Ideal R) [I.IsPrincipal] (p : Ideal R) (hp : p ∈ I.minimalPrimes) : p.height ≤ 1 := by
-  have := hp.1.1
+  have := Ideal.minimalPrimes_isPrime hp
   let f := algebraMap R (Localization.AtPrime p)
   have := Ideal.height_le_one_of_isPrincipal_of_mem_minimalPrimes_of_isLocalRing (I.map f) ?_
   · rwa [← IsLocalization.height_comap p.primeCompl,
@@ -117,14 +117,15 @@ lemma Ideal.height_le_one_of_isPrincipal_of_mem_minimalPrimes
 theorem Ideal.map_height_le_one_of_mem_minimalPrimes {I p : Ideal R} {x : R}
     (hp : p ∈ (I ⊔ span {x}).minimalPrimes) : (p.map (Ideal.Quotient.mk I)).height ≤ 1 :=
   let f := Ideal.Quotient.mk I
-  have : p.IsPrime := hp.1.1
-  have hfp : RingHom.ker f ≤ p := I.mk_ker.trans_le (le_sup_left.trans hp.1.2)
+  have : p.IsPrime := Ideal.minimalPrimes_isPrime hp
+  have hfp : RingHom.ker f ≤ p := I.mk_ker.trans_le (le_sup_left.trans (Ideal.le_minimalPrimes hp))
   height_le_one_of_isPrincipal_of_mem_minimalPrimes ((span {x}).map f) (p.map f)
-    ⟨⟨map_isPrime_of_surjective Quotient.mk_surjective hfp, map_mono (le_sup_right.trans hp.1.2)⟩,
-      fun _ ⟨hr, hxr⟩ hrp ↦ map_le_iff_le_comap.mpr <| hp.2 ⟨hr.comap f, sup_le_iff.mpr
-        ⟨I.mk_ker.symm.trans_le <| ker_le_comap (Ideal.Quotient.mk I), le_comap_of_map_le hxr⟩⟩ <|
-          (comap_mono hrp).trans <| Eq.le <|
-            (p.comap_map_of_surjective _ Quotient.mk_surjective).trans <| sup_eq_left.mpr hfp⟩
+    ⟨⟨map_isPrime_of_surjective Quotient.mk_surjective hfp,
+      map_mono (le_sup_right.trans (Ideal.le_minimalPrimes hp))⟩,
+        fun _ ⟨hr, hxr⟩ hrp ↦ map_le_iff_le_comap.mpr <| hp.2 ⟨hr.comap f, sup_le_iff.mpr
+          ⟨I.mk_ker.symm.trans_le <| ker_le_comap (Ideal.Quotient.mk I), le_comap_of_map_le hxr⟩⟩ <|
+            (comap_mono hrp).trans <| Eq.le <|
+              (p.comap_map_of_surjective _ Quotient.mk_surjective).trans <| sup_eq_left.mpr hfp⟩
 
 /-- If `q < p` are prime ideals such that `p` is minimal over `span (s ∪ {x})` and
 `t` is a set contained in `q` such that `s ⊆ √span (t ∪ {x})`, then `q` is minimal over `span t`.
@@ -152,7 +153,8 @@ theorem Ideal.mem_minimalPrimes_span_of_mem_minimalPrimes_span_insert {q p : Ide
     rwa [comap_map_of_surjective f hf, ← RingHom.ker_eq_comap_bot,
       mk_ker, sup_eq_left.mpr hI'q] at this
   refine height_le_one_of_isPrincipal_of_mem_minimalPrimes ((span {x}).map f) (p.map f) ⟨⟨this,
-    map_mono <| span_le.mpr <| Set.singleton_subset_iff.mpr <| hp.1.2 <| subset_span <| .inl rfl⟩,
+    map_mono <| span_le.mpr <| Set.singleton_subset_iff.mpr <| (Ideal.le_minimalPrimes hp) <|
+      subset_span <| .inl rfl⟩,
     fun r ⟨hr, hxr⟩ hrp ↦ map_le_iff_le_comap.mpr (hp.2 ⟨hr.comap f, ?_⟩ ?_)⟩
   · rw [span_le, Set.insert_subset_iff]
     have := map_le_iff_le_comap.mp hxr (subset_span rfl)
@@ -176,7 +178,7 @@ nonrec lemma Ideal.height_le_spanRank_toENat_of_mem_minimal_primes
   induction hn : s.card using Nat.strong_induction_on generalizing R with
   | h n H =>
     replace hn : s.card ≤ n := hn.le
-    have := hp.1.1
+    have := Ideal.minimalPrimes_isPrime hp
     cases n with
     | zero =>
       rw [ENat.coe_zero, nonpos_iff_eq_zero, height_eq_primeHeight p,
@@ -204,7 +206,7 @@ nonrec lemma Ideal.height_le_spanRank_toENat_of_mem_minimal_primes
           ⟨le_sup_left, x, mem_sup_right (mem_span_singleton_self _), hxq⟩).trans_le hJ)
           ((le_maximalIdeal hJ'.ne_top).lt_of_not_ge h)
       have h : (s' : Set R) ⊆ (q ⊔ span {x}).radical := by
-        have := hp.1.2.trans this
+        have := (Ideal.le_minimalPrimes hp).trans this
         rw [span_le, Finset.coe_insert, Set.insert_subset_iff] at this
         exact this.2
       obtain ⟨t, ht, hspan⟩ := exists_subset_radical_span_sup_of_subset_radical_sup _ _ _ h
@@ -239,7 +241,7 @@ lemma Ideal.height_le_spanRank_toENat (I : Ideal R) (hI : I ≠ ⊤) :
   obtain ⟨J, hJ⟩ := nonempty_minimalPrimes hI
   refine (iInf₂_le J hJ).trans ?_
   convert (I.height_le_spanRank_toENat_of_mem_minimal_primes J hJ)
-  exact Eq.symm (@height_eq_primeHeight _ _ J hJ.1.1)
+  exact (@height_eq_primeHeight _ _ J (Ideal.minimalPrimes_isPrime hJ)).symm
 
 lemma Ideal.height_le_spanFinrank (I : Ideal R) (hI : I ≠ ⊤) :
     I.height ≤ I.spanFinrank := by
@@ -318,7 +320,8 @@ lemma Ideal.height_le_height_add_spanFinrank_of_le {I p : Ideal R} [p.IsPrime] (
   let p' := p.map (algebraMap R (R ⧸ I))
   have : p'.IsPrime := isPrime_map_quotientMk_of_isPrime hrp
   obtain ⟨s, hps, hs⟩ := exists_finset_card_eq_height_of_isNoetherianRing p'
-  have hsp' : (s : Set (R ⧸ I)) ⊆ (p' : Set _) := fun _ hx ↦ hps.1.2 (subset_span hx)
+  have hsp' : (s : Set (R ⧸ I)) ⊆ (p' : Set _) :=
+    fun _ hx ↦ (Ideal.le_minimalPrimes hps) (subset_span hx)
   have : Set.SurjOn (Ideal.Quotient.mk I) p s := by
     refine Set.SurjOn.mono subset_rfl hsp' fun x hx ↦ ?_
     obtain ⟨x, rfl⟩ := Ideal.Quotient.mk_surjective x
@@ -415,7 +418,7 @@ lemma Ideal.height_le_height_add_of_liesOver [IsNoetherianRing S] (p : Ideal R)
   let P' := P.map (Ideal.Quotient.mk <| p.map (algebraMap R S))
   obtain ⟨s', hP', heq'⟩ := P'.exists_finset_card_eq_height_of_isNoetherianRing
   have hsP'sub : (s' : Set <| S ⧸ (Ideal.map (algebraMap R S) p)) ⊆ (P' : Set <| S ⧸ _) :=
-    fun x hx ↦ hP'.1.2 (Ideal.subset_span hx)
+    fun x hx ↦ (Ideal.le_minimalPrimes hP') (Ideal.subset_span hx)
   have : Set.SurjOn (Ideal.Quotient.mk (p.map (algebraMap R S))) P s' := by
     refine Set.SurjOn.mono subset_rfl hsP'sub fun x hx ↦ ?_
     obtain ⟨y, rfl⟩ := Ideal.Quotient.mk_surjective x

Mathlib/RingTheory/Ideal/MinimalPrime/Basic.lean

@@ -54,6 +54,12 @@ variable {I J}
 theorem Ideal.minimalPrimes_isPrime {p : Ideal R} (h : p ∈ I.minimalPrimes) : p.IsPrime :=
   h.1.1
 
+theorem Ideal.le_minimalPrimes {p : Ideal R} (h : p ∈ I.minimalPrimes) : I ≤ p :=
+  h.1.2
+
+theorem minimalPrimes_isPrime {p : Ideal R} (h : p ∈ minimalPrimes R) : p.IsPrime :=
+  h.1.1
+
 theorem Ideal.exists_minimalPrimes_le [J.IsPrime] (e : I ≤ J) : ∃ p ∈ I.minimalPrimes, p ≤ J := by
   set S := { p : (Ideal R)ᵒᵈ | Ideal.IsPrime p ∧ I ≤ OrderDual.ofDual p }
   suffices h : ∃ m, OrderDual.toDual J ≤ m ∧ Maximal (· ∈ S) m by
@@ -117,17 +123,17 @@ theorem Ideal.minimalPrimes_eq_subsingleton (hI : I.IsPrimary) : I.minimalPrimes
   ext J
   constructor
   · exact fun H =>
-      let e := H.1.1.radical_le_iff.mpr H.1.2
+      let e := (Ideal.minimalPrimes_isPrime H).radical_le_iff.mpr (Ideal.le_minimalPrimes H)
       (H.2 ⟨Ideal.isPrime_radical hI, Ideal.le_radical⟩ e).antisymm e
   · rintro (rfl : J = I.radical)
     exact ⟨⟨Ideal.isPrime_radical hI, Ideal.le_radical⟩, fun _ H _ => H.1.radical_le_iff.mpr H.2⟩
 
 theorem Ideal.minimalPrimes_eq_subsingleton_self [I.IsPrime] : I.minimalPrimes = {I} := by
   ext J
-  constructor
-  · exact fun H => (H.2 ⟨inferInstance, rfl.le⟩ H.1.2).antisymm H.1.2
-  · rintro (rfl : J = I)
-    exact ⟨⟨inferInstance, rfl.le⟩, fun _ h _ => h.2⟩
+  refine ⟨fun H => (H.2 ⟨inferInstance, rfl.le⟩ (Ideal.le_minimalPrimes H)).antisymm
+    (Ideal.le_minimalPrimes H), ?_⟩
+  rintro (rfl : J = I)
+  exact ⟨⟨inferInstance, rfl.le⟩, fun _ h _ => h.2⟩
 
 variable (R) in
 theorem IsDomain.minimalPrimes_eq_singleton_bot [IsDomain R] :
@@ -144,7 +150,7 @@ theorem Ideal.minimalPrimes_top : (⊤ : Ideal R).minimalPrimes = ∅ := by
   ext p
   simp only [Set.notMem_empty, iff_false]
   intro h
-  exact h.1.1.ne_top (top_le_iff.mp h.1.2)
+  exact (Ideal.minimalPrimes_isPrime h).ne_top (top_le_iff.mp (Ideal.le_minimalPrimes h))
 
 theorem Ideal.minimalPrimes_eq_empty_iff (I : Ideal R) :
     I.minimalPrimes = ∅ ↔ I = ⊤ := by
@@ -163,7 +169,8 @@ lemma Ideal.mem_minimalPrimes_sup {R : Type*} [CommRing R] {p I J : Ideal R} [p.
     p ∈ (I ⊔ J).minimalPrimes := by
   refine ⟨⟨‹_›, ?_⟩, fun q ⟨_, hq⟩ hqp ↦ ?_⟩
   · rw [sup_le_iff]
-    exact ⟨hle, by simpa [hle] using Ideal.comap_mono (f := Ideal.Quotient.mk I) h.1.2⟩
+    refine ⟨hle, ?_⟩
+    simpa [hle] using Ideal.comap_mono (f := Ideal.Quotient.mk I) (Ideal.le_minimalPrimes h)
   · rw [sup_le_iff] at hq
     have h2 : p.map (Quotient.mk I) ≤ q.map (Quotient.mk I) :=
       h.2 ⟨isPrime_map_quotientMk_of_isPrime hq.1, map_mono hq.2⟩ (map_mono hqp)
@@ -183,7 +190,7 @@ lemma Ideal.map_sup_mem_minimalPrimes_of_map_quotientMk_mem_minimalPrimes
   refine ⟨⟨inferInstance, sup_le_iff.mpr ?_⟩, fun q ⟨_, hleq⟩ hqle ↦ ?_⟩
   · refine ⟨?_, hJP⟩
     rw [Ideal.map_le_iff_le_comap, ← Ideal.under_def, ← Ideal.over_def P p]
-    exact hI.1.2
+    exact Ideal.le_minimalPrimes hI
   · simp only [sup_le_iff] at hleq
     have h1 : p.map (algebraMap R S) ≤ q := by
       rw [Ideal.map_le_iff_le_comap]

Mathlib/RingTheory/Ideal/MinimalPrime/Colon.lean

@@ -48,7 +48,8 @@ theorem exists_eq_colon_of_mem_minimalPrimes [IsNoetherianRing R]
     refine ⟨n, hn0, ((h.toFinset.erase I).inf id) ^ n, hn, ?_⟩
     have (K : Ideal R) (hKI : K ≤ I) (hK : K ∈ ann.minimalPrimes) : K = I :=
       le_antisymm hKI (hI.2 hK.1 hKI)
-    simpa [hI.1.1.pow_le_iff hn0, hI.1.1.inf_le', imp_not_comm, not_imp_not]
+    simpa [(Ideal.minimalPrimes_isPrime hI).pow_le_iff hn0,
+      (Ideal.minimalPrimes_isPrime hI).inf_le', imp_not_comm, not_imp_not]
   obtain ⟨hn0, J, hJ, hJI⟩ := Nat.find_spec key
   -- let `n` be minimal such that there exists an ideal `J` with `I ^ n * J ≤ ann` and `¬ J ≠ I`
   set n := Nat.find key
@@ -74,9 +75,7 @@ theorem exists_eq_colon_of_mem_minimalPrimes [IsNoetherianRing R]
   -- let `z` be the product of these finitely many `f y`'s
   let z := ∏ y ∈ s, f y
   -- then `z ∉ I`
-  have hz : z ∉ I := by
-    simp only [z, hI.1.1.prod_mem_iff, not_exists, not_and_or]
-    exact fun i ↦ Or.inr (h i)
+  have hz : z ∉ I := by simp [z, (Ideal.minimalPrimes_isPrime hI).prod_mem_iff, h]
   -- and `K ≤ colon N {z • x}`
   have hz' : K ≤ colon N {z • x} := by
     rw [← (map_injective_of_injective K.subtype_injective).eq_iff, map_subtype_top] at hs
@@ -92,11 +91,12 @@ theorem exists_eq_colon_of_mem_minimalPrimes [IsNoetherianRing R]
     simpa only [ann, mem_colon_singleton, mul_comm, mul_smul] using hz' hi
   -- but now `K = I ^ (n - 1) * J` contradicts the minimality of `n`
   have hK : I ^ (n - 1) * (J * Ideal.span {z}) ≤ ann ∧ ¬ J * Ideal.span {z} ≤ I := by
-    rw [← mul_assoc, hI.1.1.mul_le, not_or, Ideal.span_singleton_le_iff_mem]
+    rw [← mul_assoc, (Ideal.minimalPrimes_isPrime hI).mul_le, not_or,
+      Ideal.span_singleton_le_iff_mem]
     exact ⟨hz', hJI, hz⟩
   by_cases hn' : n - 1 = 0
   · simp [K, show n = 1 by grind] at hz'
-    exact (hK.2 (hz'.trans hI.1.2)).elim
+    exact (hK.2 (hz'.trans (Ideal.le_minimalPrimes hI))).elim
   · grind [Nat.find_min' key ⟨hn', J * Ideal.span {z}, hK⟩]
 
 end Submodule