[plt-scheme] How to make the following code more clear?

> #lang typed-scheme
> [...]
> (: largest ((cons α (Listof α)) -> α))
> ;; pick the largest value from the list
> (define (largest lst)
>   (foldr max (car lst) (cdr lst)))

any reason why you used (cons a (Listof a)) instead of simply (Listof  
a) in the type signature of largest?

-- Éric