simp only [if_pos h1]
zs : List String
X : String
vs : List Var
j : ℕ
a1 : bound_ 0 ∈ vs
h1 : 0 < j
⊢ (if 0 < j then bound_ 0
    else
      if x : 0 - j < (List.map free_ zs).length then (List.map free_ zs)[0 - j]
      else bound_ (0 - j - (List.map free_ zs).length + j)) =
    bound_ 0
no goals