case nil =>
  simp at h1
α : Type
inst✝ : DecidableEq α
xs_hd : α
xs_tl : List α
xs_ih : ∀ (ys : List α), xs_tl.length = ys.length → xs_tl.Nodup → ys.Nodup → ∃ f, InjOn f xs_tl ∧ map f xs_tl = ys
h2 : (xs_hd :: xs_tl).Nodup
h1 : (xs_hd :: xs_tl).length = [].length
h3 : [].Nodup
⊢ ∃ f, InjOn f (xs_hd :: xs_tl) ∧ map f (xs_hd :: xs_tl) = []
no goals