"Cannot find to_s using type inference" on id.to_s?

Quick Q:

I've overriden to _to param method in some of my rails' project's models for more declarative urls with the following code:


  def to_param
    [id.to_s, permalink] * '-'
  end

No Rubymine whines about the .to_s part with the message above. I mean, it's not really an error, but I should be able to use the integer.to_s method, right?

-J