unnecessary (require 'cus-edit) in set-variable?

[Drew Adams]

The definition of `set-variable' contains this code:

(let ((type (get variable 'custom-type)))
    (when type
      ;; Match with custom type.
      (require 'cus-edit)
      (setq type (widget-convert type))
      (unless (widget-apply type :match value)
 (error "Value `%S' does not match type %S of %S"
        value (car type) variable))))

I don't understand the (require 'cus-edit), since there is nothing in
cus-edit.el that is called here.  Should it be removed? If not, why
is it needed?