Guide: functions

Just a few words about functions and defining them.
I've been wondering about the style guidelines here; e.g. if exceptions should be made for cases where after the `return blah` one has some `fn` item declarations that are used by the code above; or even just the cases where the function body is long and so one uses `return` just to emphasize that you've got to the end.

Anyway, I'll agree that it is poor style in this example, so I guess this comment can stay as it is.