rfl
case refl
α : Type u_1
p✝¹ : α → Prop
inst✝² : DecidablePred p✝¹
p✝ : α → Prop
inst✝¹ : DecidablePred p✝
p : α → Prop
inst✝ : DecidablePred p
x : α
xs : List α
h : p x
i : (List.sublist p xs).Index
x✝ : (⟨x, ⋯⟩ :: List.sublist p xs).Index
⊢ (unsublist p i).tail = (unsublist p i).tail
no goals