As another answer says, only an actual inventor or someone an actual inventor has assigned their rights to can legally file in the U.S. since the AIA went into effect the declaration has been changed to
I believe that I am the original inventor or an original joint inventor of a claimed invention in the application.
If the disclosure would not be considered confidential it did start a one year clock on when you can file. Also, as mentioned, if you both file and he files first you need to prove he derived it from you. Maybe worse, he can invent something different, inspired by what he leaned from you.