Many, many years ago I was teaching a class about conditional sentences. I uttered the authoritative words, "We NEVER use
will (or
'll) in the
if-clause". I was heartened to see my students writing down this helpful rule. I was less heartened a few moments later when one of my students asked me why I frequently said, "
If you'll leave your homework on my desk as you go, I'll get it back to you tomorrow".
Since that day I have never used the words 'never' or 'always' when giving "rules" ;-). And I have tried to check my facts thoroughly
before giving "rules".