{
  apply List.eq_nil_of_length_eq_zero
  simp only [← h1]
  simp
}
case s1
α : Type
inst✝ : DecidableEq α
ys : List α
h1 : [].length = ys.length
h2 : [].Nodup
h3 : ys.Nodup
⊢ ys = []

α : Type
inst✝ : DecidableEq α
ys : List α
h1 : [].length = ys.length
h2 : [].Nodup
h3 : ys.Nodup
s1 : ys = []
⊢ ∃ f, InjOn f [] ∧ map f [] = ys
α : Type
inst✝ : DecidableEq α
ys : List α
h1 : [].length = ys.length
h2 : [].Nodup
h3 : ys.Nodup
s1 : ys = []
⊢ ∃ f, InjOn f [] ∧ map f [] = ys