Post a comment and log in at the same time

I’d like to be able to offer the ability to post a comment and log in at the same time. I.e., if a user is logged out, they can enter their comment and click submit, then be asked for their username and password, and upon submit be taken to their posted comment. Does anyone know of a plugin that will make this happen?

Currently: A user has to login before they can view and submit the comment form Desired: User can view the comment form and upon submit, type in their name and password and be logged in with the comment posted.