Strong Typing (not the usual 'why' thread)

So i did see the post about typing in the sticky above, but my question isnt as to why i should use it. I had heard that with as3 it was Required that you give a type to all your variables or it wouldn’t compile. I have found this to be false which gave rise to my question. Did i just mishear it altogether or is there perhaps an option that can be switched so that the typing is required? This was born out or curiosity than anything else, any insight would be appreciated. thanks.