Am I just a naive IO user, or is this a bug?

[DCP at MIT-MC (David C. Plummer)]

File foo is freshly opened for input, but there is nothing in the
file. Now I do either a 

(tyi foo)   ==> -1
or
(readline foo 'nil) ==> nil

This is right, but try to do another tyi or readline
and you will find that the file has been graciously
closed behind your back. You cannot attempt to read
from it and request more end-of-file conditions.

what gives??