Module: Mathlib.RingTheory.Spectrum.Prime.ChevalleyComplexity

Goal state before:
pp: case left
R : Type u_2
inst✝ : CommRing R
m n : ℕ
f : MvPolynomial (Fin n) R →ₐ[R] MvPolynomial (Fin m) R
k : ℕ
d : Multiset (Fin m)
S : ConstructibleSetData (MvPolynomial (Fin m) R)
hSn : ∀ C ∈ S, C.n ≤ k
hS : ∀ C ∈ S, ∀ (j : Fin C.n), (C.g j).degrees ≤ d
hf : ∀ (i : Fin n), (f (MvPolynomial.X i)).degrees ≤ d
g : MvPolynomial (Fin m) (MvPolynomial (Fin n) R) →+* MvPolynomial (Fin m) R := ⋯
hg : g.comp (algebraMap (MvPolynomial (Fin n) R) (MvPolynomial (Fin m) (MvPolynomial (Fin n) R))) = ↑f
σ : MvPolynomial (Fin m) R →+* MvPolynomial (Fin m) (MvPolynomial (Fin n) R) := ⋯
hσ : g.comp σ = RingHom.id (MvPolynomial (Fin m) R)
hσ' : ∀ (x : MvPolynomial (Fin m) R), g (σ x) = x
hg' : Surjective ⇑g
S' : ConstructibleSetData (MvPolynomial (Fin m) (MvPolynomial (Fin n) R)) := ⋯
s₀ : Set (MvPolynomial (Fin m) (MvPolynomial (Fin n) R)) := ⋯
hs : zeroLocus s₀ = Set.range (comap g)
hg'' : ∀ (t : Set (PrimeSpectrum (MvPolynomial (Fin m) R))), comap g '' t = comap σ ⁻¹' t ∩ zeroLocus s₀
hS' : comap g '' S.toSet = S'.toSet
x : BasicConstructibleSetData (MvPolynomial (Fin m) R)
hx : x ∈ S
j : Fin x.n ⊕ Fin n
⊢ ∀ (i : Fin m →₀ ℕ),
    (MvPolynomial.coeff i
          (Sum.elim (⇑σ ∘ x.g) (fun i ↦ MvPolynomial.C (MvPolynomial.X i) - σ (f (MvPolynomial.X i))) j)).degrees ≤
      Finset.univ.val

pp: case right
R : Type u_2
inst✝ : CommRing R
m n : ℕ
f : MvPolynomial (Fin n) R →ₐ[R] MvPolynomial (Fin m) R
k : ℕ
d : Multiset (Fin m)
S : ConstructibleSetData (MvPolynomial (Fin m) R)
hSn : ∀ C ∈ S, C.n ≤ k
hS : ∀ C ∈ S, ∀ (j : Fin C.n), (C.g j).degrees ≤ d
hf : ∀ (i : Fin n), (f (MvPolynomial.X i)).degrees ≤ d
g : MvPolynomial (Fin m) (MvPolynomial (Fin n) R) →+* MvPolynomial (Fin m) R := ⋯
hg : g.comp (algebraMap (MvPolynomial (Fin n) R) (MvPolynomial (Fin m) (MvPolynomial (Fin n) R))) = ↑f
σ : MvPolynomial (Fin m) R →+* MvPolynomial (Fin m) (MvPolynomial (Fin n) R) := ⋯
hσ : g.comp σ = RingHom.id (MvPolynomial (Fin m) R)
hσ' : ∀ (x : MvPolynomial (Fin m) R), g (σ x) = x
hg' : Surjective ⇑g
S' : ConstructibleSetData (MvPolynomial (Fin m) (MvPolynomial (Fin n) R)) := ⋯
s₀ : Set (MvPolynomial (Fin m) (MvPolynomial (Fin n) R)) := ⋯
hs : zeroLocus s₀ = Set.range (comap g)
hg'' : ∀ (t : Set (PrimeSpectrum (MvPolynomial (Fin m) R))), comap g '' t = comap σ ⁻¹' t ∩ zeroLocus s₀
hS' : comap g '' S.toSet = S'.toSet
x : BasicConstructibleSetData (MvPolynomial (Fin m) R)
hx : x ∈ S
j : Fin x.n ⊕ Fin n
⊢ (Sum.elim (⇑σ ∘ x.g) (fun i ↦ MvPolynomial.C (MvPolynomial.X i) - σ (f (MvPolynomial.X i))) j).degrees ≤ d

Tactic:
· intro i
        obtain j | j := j
        · simp [σ, MvPolynomial.coeff_map, degrees_C]
        · simp only [MvPolynomial.algebraMap_eq, Sum.elim_inr, MvPolynomial.coeff_sub,
            MvPolynomial.coeff_C, MvPolynomial.coeff_map, σ]
          refine degrees_sub_le.trans ?_
          simp only [degrees_C, apply_ite, degrees_zero,
            Multiset.union_zero]
          split_ifs with h
          · refine (degrees_X' _).trans ?_
            simp
          · simp

Goal state after:
case right
R : Type u_2
inst✝ : CommRing R
m n : ℕ
f : MvPolynomial (Fin n) R →ₐ[R] MvPolynomial (Fin m) R
k : ℕ
d : Multiset (Fin m)
S : ConstructibleSetData (MvPolynomial (Fin m) R)
hSn : ∀ C ∈ S, C.n ≤ k
hS : ∀ C ∈ S, ∀ (j : Fin C.n), (C.g j).degrees ≤ d
hf : ∀ (i : Fin n), (f (MvPolynomial.X i)).degrees ≤ d
g : MvPolynomial (Fin m) (MvPolynomial (Fin n) R) →+* MvPolynomial (Fin m) R := ⋯
hg : g.comp (algebraMap (MvPolynomial (Fin n) R) (MvPolynomial (Fin m) (MvPolynomial (Fin n) R))) = ↑f
σ : MvPolynomial (Fin m) R →+* MvPolynomial (Fin m) (MvPolynomial (Fin n) R) := ⋯
hσ : g.comp σ = RingHom.id (MvPolynomial (Fin m) R)
hσ' : ∀ (x : MvPolynomial (Fin m) R), g (σ x) = x
hg' : Surjective ⇑g
S' : ConstructibleSetData (MvPolynomial (Fin m) (MvPolynomial (Fin n) R)) := ⋯
s₀ : Set (MvPolynomial (Fin m) (MvPolynomial (Fin n) R)) := ⋯
hs : zeroLocus s₀ = Set.range (comap g)
hg'' : ∀ (t : Set (PrimeSpectrum (MvPolynomial (Fin m) R))), comap g '' t = comap σ ⁻¹' t ∩ zeroLocus s₀
hS' : comap g '' S.toSet = S'.toSet
x : BasicConstructibleSetData (MvPolynomial (Fin m) R)
hx : x ∈ S
j : Fin x.n ⊕ Fin n
⊢ (Sum.elim (⇑σ ∘ x.g) (fun i ↦ MvPolynomial.C (MvPolynomial.X i) - σ (f (MvPolynomial.X i))) j).degrees ≤ d