-- Lean 4 proof step from Mathlib.Algebra.Category.ModuleCat.Stalk (goal)
Goal:
C : Type u_1
inst : SmallCategory C
inst_1 : IsFiltered C
R : C ⥤ RingCat
M : C ⥤ Ab
inst_2 : (i : C) → Module (↑(R.obj i) : Type (max u_1 u_2)) (↑(M.obj i) : Type (max u_1 u_3))
H :
  ∀ {i j : C} (f : i ⟶ j) (r : (↑(R.obj i) : Type (max u_1 u_2))) (m : (↑(M.obj i) : Type (max u_1 u_3))),
    (ConcreteCategory.hom (FC := fun (x1 x2 : AddCommGrpCat) ↦ (↑x1 : Type (max u_1 u_3)) →+ (↑x2 : Type (max u_1 u_3)))
            (CC := AddCommGrpCat.carrier) (M.map f) :
          (a : (↑(M.obj i) : Type (max u_1 u_3))) → (↑(M.obj j) : Type (max u_1 u_3)))
        (r • m) =
      HSMul.hSMul (α := (↑(R.obj j) : Type (max u_1 u_2))) (β := (↑(M.obj j) : Type (max u_1 u_3)))
        ((ConcreteCategory.hom (FC := fun (R S : RingCat) ↦ (↑R : Type (max u_1 u_2)) →+* (↑S : Type (max u_1 u_2)))
                (CC := RingCat.carrier) (R.map f) :
              (a : (↑(R.obj i) : Type (max u_1 u_2))) → (↑(R.obj j) : Type (max u_1 u_2)))
            r :
          (↑(R.obj j) : Type (max u_1 u_2)))
        ((ConcreteCategory.hom (FC := fun (x1 x2 : AddCommGrpCat) ↦
                (↑x1 : Type (max u_1 u_3)) →+ (↑x2 : Type (max u_1 u_3))) (CC := AddCommGrpCat.carrier) (M.map f) :
              (a : (↑(M.obj i) : Type (max u_1 u_3))) → (↑(M.obj j) : Type (max u_1 u_3)))
            m :
          (↑(M.obj j) : Type (max u_1 u_3)))
m : (↑(AddCommGrpCat.FilteredColimits.colimit.{u_1, u_3} M) : Type (max u_1 u_3))
V : C
b :
  (((M ⋙
            forget₂ AddCommGrpCat (FC := fun (x1 x2 : AddCommGrpCat) ↦
              (↑x1 : Type (max u_3 u_1)) →+ (↑x2 : Type (max u_3 u_1))) (CC := AddCommGrpCat.carrier) AddGrpCat (FD :=
              fun (x1 x2 : AddGrpCat) ↦ (↑x1 : Type (max u_3 u_1)) →+ (↑x2 : Type (max u_3 u_1))) (CD :=
              AddGrpCat.carrier)) ⋙
          forget₂ AddGrpCat (FC := fun (x1 x2 : AddGrpCat) ↦ (↑x1 : Type (max u_3 u_1)) →+ (↑x2 : Type (max u_3 u_1)))
            (CC := AddGrpCat.carrier) AddMonCat (FD := fun (x1 x2 : AddMonCat) ↦
            (↑x1 : Type (max u_3 u_1)) →+ (↑x2 : Type (max u_3 u_1))) (CD := AddMonCat.carrier)) ⋙
        forget AddMonCat (FC := fun (x1 x2 : AddMonCat) ↦ (↑x1 : Type (max u_3 u_1)) →+ (↑x2 : Type (max u_3 u_1)))
          (CC := AddMonCat.carrier)).obj
    V
⊢ HSMul.hSMul (α := (↑(RingCat.FilteredColimits.colimit.{u_1, u_2} R) : Type (max u_1 u_2))) 1
      (Quot.mk
        (((M ⋙
                forget₂ AddCommGrpCat (FC := fun (x1 x2 : AddCommGrpCat) ↦
                  (↑x1 : Type (max u_3 u_1)) →+ (↑x2 : Type (max u_3 u_1))) (CC := AddCommGrpCat.carrier) AddGrpCat
                  (FD := fun (x1 x2 : AddGrpCat) ↦ (↑x1 : Type (max u_3 u_1)) →+ (↑x2 : Type (max u_3 u_1))) (CD :=
                  AddGrpCat.carrier)) ⋙
              forget₂ AddGrpCat (FC := fun (x1 x2 : AddGrpCat) ↦
                (↑x1 : Type (max u_3 u_1)) →+ (↑x2 : Type (max u_3 u_1))) (CC := AddGrpCat.carrier) AddMonCat (FD :=
                fun (x1 x2 : AddMonCat) ↦ (↑x1 : Type (max u_3 u_1)) →+ (↑x2 : Type (max u_3 u_1))) (CD :=
                AddMonCat.carrier)) ⋙
            forget AddMonCat (FC := fun (x1 x2 : AddMonCat) ↦ (↑x1 : Type (max u_3 u_1)) →+ (↑x2 : Type (max u_3 u_1)))
              (CC := AddMonCat.carrier)).ColimitTypeRel
        (Sigma.mk (β := fun (j : C) ↦
          (((M ⋙
                    forget₂ AddCommGrpCat (FC := fun (x1 x2 : AddCommGrpCat) ↦
                      (↑x1 : Type (max u_3 u_1)) →+ (↑x2 : Type (max u_3 u_1))) (CC := AddCommGrpCat.carrier) AddGrpCat
                      (FD := fun (x1 x2 : AddGrpCat) ↦ (↑x1 : Type (max u_3 u_1)) →+ (↑x2 : Type (max u_3 u_1))) (CD :=
                      AddGrpCat.carrier)) ⋙
                  forget₂ AddGrpCat (FC := fun (x1 x2 : AddGrpCat) ↦
                    (↑x1 : Type (max u_3 u_1)) →+ (↑x2 : Type (max u_3 u_1))) (CC := AddGrpCat.carrier) AddMonCat (FD :=
                    fun (x1 x2 : AddMonCat) ↦ (↑x1 : Type (max u_3 u_1)) →+ (↑x2 : Type (max u_3 u_1))) (CD :=
                    AddMonCat.carrier)) ⋙
                forget AddMonCat (FC := fun (x1 x2 : AddMonCat) ↦
                  (↑x1 : Type (max u_3 u_1)) →+ (↑x2 : Type (max u_3 u_1))) (CC := AddMonCat.carrier)).obj
            j)
          V b)) =
    Quot.mk
      (((M ⋙
              forget₂ AddCommGrpCat (FC := fun (x1 x2 : AddCommGrpCat) ↦
                (↑x1 : Type (max u_3 u_1)) →+ (↑x2 : Type (max u_3 u_1))) (CC := AddCommGrpCat.carrier) AddGrpCat (FD :=
                fun (x1 x2 : AddGrpCat) ↦ (↑x1 : Type (max u_3 u_1)) →+ (↑x2 : Type (max u_3 u_1))) (CD :=
                AddGrpCat.carrier)) ⋙
            forget₂ AddGrpCat (FC := fun (x1 x2 : AddGrpCat) ↦ (↑x1 : Type (max u_3 u_1)) →+ (↑x2 : Type (max u_3 u_1)))
              (CC := AddGrpCat.carrier) AddMonCat (FD := fun (x1 x2 : AddMonCat) ↦
              (↑x1 : Type (max u_3 u_1)) →+ (↑x2 : Type (max u_3 u_1))) (CD := AddMonCat.carrier)) ⋙
          forget AddMonCat (FC := fun (x1 x2 : AddMonCat) ↦ (↑x1 : Type (max u_3 u_1)) →+ (↑x2 : Type (max u_3 u_1)))
            (CC := AddMonCat.carrier)).ColimitTypeRel
      (Sigma.mk (β := fun (j : C) ↦
        (((M ⋙
                  forget₂ AddCommGrpCat (FC := fun (x1 x2 : AddCommGrpCat) ↦
                    (↑x1 : Type (max u_3 u_1)) →+ (↑x2 : Type (max u_3 u_1))) (CC := AddCommGrpCat.carrier) AddGrpCat
                    (FD := fun (x1 x2 : AddGrpCat) ↦ (↑x1 : Type (max u_3 u_1)) →+ (↑x2 : Type (max u_3 u_1))) (CD :=
                    AddGrpCat.carrier)) ⋙
                forget₂ AddGrpCat (FC := fun (x1 x2 : AddGrpCat) ↦
                  (↑x1 : Type (max u_3 u_1)) →+ (↑x2 : Type (max u_3 u_1))) (CC := AddGrpCat.carrier) AddMonCat (FD :=
                  fun (x1 x2 : AddMonCat) ↦ (↑x1 : Type (max u_3 u_1)) →+ (↑x2 : Type (max u_3 u_1))) (CD :=
                  AddMonCat.carrier)) ⋙
              forget AddMonCat (FC := fun (x1 x2 : AddMonCat) ↦
                (↑x1 : Type (max u_3 u_1)) →+ (↑x2 : Type (max u_3 u_1))) (CC := AddMonCat.carrier)).obj
          j)
        V b)
have refine : failed to pretty print expression (use 'set_option pp.rawOnError true' for raw representation)
Tactic: refine Functor.ιColimitType_eq_of_map_eq_map _ _ _ (𝟙 _) (rightToMax _ _) ?_