refine (inter_subset_inter (M.subset_cl _ (hIs i).subset_ground)
  (M.subset_cl _ (hIs j).subset_ground)).trans ?_
case refine_2
ι : Type u_1
α : Type u_2
M : Matroid α
B I J X X' Y Y' F : Set α
Xs Ys Js Is : ι → Set α
i✝ j✝ : ι
e f : α
hI : M.Indep (⋃ i, Is i)
hdj : Pairwise (Disjoint on Is)
hIs : ∀ (i : ι), M.Basis (Is i) (Xs i)
i j : ι
hij : i ≠ j
⊢ Xs i ∩ Xs j ⊆ M.cl ∅
case refine_2
ι : Type u_1
α : Type u_2
M : Matroid α
B I J X X' Y Y' F : Set α
Xs Ys Js Is : ι → Set α
i✝ j✝ : ι
e f : α
hI : M.Indep (⋃ i, Is i)
hdj : Pairwise (Disjoint on Is)
hIs : ∀ (i : ι), M.Basis (Is i) (Xs i)
i j : ι
hij : i ≠ j
⊢ M.cl (Xs i) ∩ M.cl (Xs j) ⊆ M.cl ∅