exact ⟨M.fundCct e I, hI.indep.fundCct_circuit ⟨h, not_mem_subset hI.subset he⟩,
  M.mem_fundCct e I, (fundCct_subset_insert _ _).trans (insert_subset_insert hI.subset)⟩
case refine'_1.intro
α : Type u_1
M : Matroid α
C C' I✝ X K C₁ C₂ R : Set α
e f x y : α
hX : autoParam (X ⊆ M.E) _auto✝
he : e ∉ X
I : Set α
h : e ∈ M.cl I
hI : M.Basis I X
⊢ ∃ C, M.Circuit C ∧ e ∈ C ∧ C ⊆ insert e X
no goals