-- Lean 4 proof step from Mathlib.LinearAlgebra.CliffordAlgebra.Contraction (goal)
Goal:
R : Type u1
inst : CommRing R
M : Type u2
inst_1 : AddCommGroup M
inst_2 : Module R M
Q : QuadraticForm R M
d d' d₁ d₂ : Module.Dual R M
x : CliffordAlgebra Q
algebraMap :
  ∀ (r : R),
    (foldr' Q (contractLeftAux Q (d₁ + d₂)) ⋯ 0 : (a : CliffordAlgebra Q) → CliffordAlgebra Q)
        ((Algebra.algebraMap R (CliffordAlgebra Q) : (a : R) → CliffordAlgebra Q) r) =
      HAdd.hAdd (α := CliffordAlgebra Q) (β := CliffordAlgebra Q)
        ((foldr' Q (contractLeftAux Q d₁) ⋯ 0 : (a : CliffordAlgebra Q) → CliffordAlgebra Q)
            ((Algebra.algebraMap R (CliffordAlgebra Q) : (a : R) → CliffordAlgebra Q) r) :
          CliffordAlgebra Q)
        ((foldr' Q (contractLeftAux Q d₂) ⋯ 0 : (a : CliffordAlgebra Q) → CliffordAlgebra Q)
            ((Algebra.algebraMap R (CliffordAlgebra Q) : (a : R) → CliffordAlgebra Q) r) :
          CliffordAlgebra Q)
add :
  ∀ (x y : CliffordAlgebra Q)
    (hx :
      (foldr' Q (contractLeftAux Q (d₁ + d₂)) ⋯ 0 : (a : CliffordAlgebra Q) → CliffordAlgebra Q) x =
        HAdd.hAdd (α := CliffordAlgebra Q) (β := CliffordAlgebra Q)
          ((foldr' Q (contractLeftAux Q d₁) ⋯ 0 : (a : CliffordAlgebra Q) → CliffordAlgebra Q) x : CliffordAlgebra Q)
          ((foldr' Q (contractLeftAux Q d₂) ⋯ 0 : (a : CliffordAlgebra Q) → CliffordAlgebra Q) x : CliffordAlgebra Q))
    (hy :
      (foldr' Q (contractLeftAux Q (d₁ + d₂)) ⋯ 0 : (a : CliffordAlgebra Q) → CliffordAlgebra Q) y =
        HAdd.hAdd (α := CliffordAlgebra Q) (β := CliffordAlgebra Q)
          ((foldr' Q (contractLeftAux Q d₁) ⋯ 0 : (a : CliffordAlgebra Q) → CliffordAlgebra Q) y : CliffordAlgebra Q)
          ((foldr' Q (contractLeftAux Q d₂) ⋯ 0 : (a : CliffordAlgebra Q) → CliffordAlgebra Q) y : CliffordAlgebra Q)),
    (foldr' Q (contractLeftAux Q (d₁ + d₂)) ⋯ 0 : (a : CliffordAlgebra Q) → CliffordAlgebra Q) (x + y) =
      HAdd.hAdd (α := CliffordAlgebra Q) (β := CliffordAlgebra Q)
        ((foldr' Q (contractLeftAux Q d₁) ⋯ 0 : (a : CliffordAlgebra Q) → CliffordAlgebra Q) (x + y) :
          CliffordAlgebra Q)
        ((foldr' Q (contractLeftAux Q d₂) ⋯ 0 : (a : CliffordAlgebra Q) → CliffordAlgebra Q) (x + y) :
          CliffordAlgebra Q)
⊢ (foldr' Q (contractLeftAux Q (d₁ + d₂)) ⋯ 0 : (a : CliffordAlgebra Q) → CliffordAlgebra Q) x =
    HAdd.hAdd (α := CliffordAlgebra Q) (β := CliffordAlgebra Q)
      ((foldr' Q (contractLeftAux Q d₁) ⋯ 0 : (a : CliffordAlgebra Q) → CliffordAlgebra Q) x : CliffordAlgebra Q)
      ((foldr' Q (contractLeftAux Q d₂) ⋯ 0 : (a : CliffordAlgebra Q) → CliffordAlgebra Q) x : CliffordAlgebra Q)
have ι_mul : ∀ (x : CliffordAlgebra Q) (m : M)
  (hx :
    (foldr' Q (contractLeftAux Q (d₁ + d₂)) sorry 0 : (a : CliffordAlgebra Q) → CliffordAlgebra Q) x =
      HAdd.hAdd (α := CliffordAlgebra Q) (β := CliffordAlgebra Q)
        ((foldr' Q (contractLeftAux Q d₁) sorry 0 : (a : CliffordAlgebra Q) → CliffordAlgebra Q) x : CliffordAlgebra Q)
        ((foldr' Q (contractLeftAux Q d₂) sorry 0 : (a : CliffordAlgebra Q) → CliffordAlgebra Q) x : CliffordAlgebra Q)),
  (foldr' Q (contractLeftAux Q (d₁ + d₂)) sorry 0 : (a : CliffordAlgebra Q) → CliffordAlgebra Q)
      (HMul.hMul (α := CliffordAlgebra Q) ((ι Q : (a : M) → CliffordAlgebra Q) m : CliffordAlgebra Q) x) =
    HAdd.hAdd (α := CliffordAlgebra Q) (β := CliffordAlgebra Q)
      ((foldr' Q (contractLeftAux Q d₁) sorry 0 : (a : CliffordAlgebra Q) → CliffordAlgebra Q)
          (HMul.hMul (α := CliffordAlgebra Q) ((ι Q : (a : M) → CliffordAlgebra Q) m : CliffordAlgebra Q) x) :
        CliffordAlgebra Q)
      ((foldr' Q (contractLeftAux Q d₂) sorry 0 : (a : CliffordAlgebra Q) → CliffordAlgebra Q)
          (HMul.hMul (α := CliffordAlgebra Q) ((ι Q : (a : M) → CliffordAlgebra Q) m : CliffordAlgebra Q) x) :
        CliffordAlgebra Q)
Tactic: induction x using CliffordAlgebra.left_induction with
      | algebraMap => simp_rw [foldr'_algebraMap, smul_zero, zero_add]
      | add _ _ hx hy => rw [map_add, map_add, map_add, add_add_add_comm, hx, hy]
      | ι_mul _ _ hx =>
        rw [foldr'_ι_mul, foldr'_ι_mul, foldr'_ι_mul, hx]
        dsimp only [contractLeftAux_apply_apply]
        rw [sub_add_sub_comm, mul_add, LinearMap.add_apply, add_smul]
Cleared hypotheses: x