rw [← hF.cl, ← cl_insert_cl_eq_cl_insert, insert_eq_of_mem heF, cl_cl]
case refine_1.intro.inr
α : Type u_1
M : Matroid α
I J B F₀ F F' X Y : Set α
e f : α
U : M.ModularCut
he : e ∉ F
heF : e ∈ M.cl F
hF : M.Flat (insert e F)
⊢ M.cl F = insert e F
no goals