Theorem: Matroid.er_empty (Matroid/Rank.lean)

State before:
α : Type u_1
ι : Type u_2
M✝ N : Matroid α
I B X X' Y Y' Z R : Set α
n : ℕ∞
e f : α
M : Matroid α
⊢ M.er ∅ = 0
Tactic:
rw [← M.empty_indep.basis_self.encard, encard_empty]
State after:
no goals