simp_rw [List.mapIdx_eq_enum_map]
α β : Type
f : ℕ → α → β
l : List α
h2 : l ≠ []
⊢ (List.mapIdx f l).getLast ⋯ = f l.dropLast.length (l.getLast h2)
α β : Type
f : ℕ → α → β
l : List α
h2 : l ≠ []
⊢ (List.map (Function.uncurry f) l.enum).getLast ⋯ = f l.dropLast.length (l.getLast h2)