reference variable before definition

[Eric Abrahamsen]

I can't tell if it's always been this way: I'm getting compiler warnings
about "reference to free variable" if the variable appears in a function
definition before it's defined in the file. So compiling this produces
warnings:

(defun make-my-day ()
  (message "It's: %s" my-day))

(defvar my-day "Monday")

Has it always been this way, and it only just got through to me? I
didn't think it was necessary to define everything before use in a
function...

Hoping I'm just hallucinating something,
Eric