A slice specifically refers to `&[T]`. A `~[T]`, as `print_all()` is declared as taking, has classically been referred to as a "vector". However, it's effectively deprecated at this point, replaced with `Vec<T>`, which is also informally called a "vector".

So the correct thing here is to replace the word "array" with "vector". A better fix is to also change `print_all()` to take `Vec<T>` instead of `~[T]`, but I understand if you consider that out of scope.