What do you do if 'a.<tab>' doesn't work because it's not 'a.fun(b, c)' but 'b.fun(a, c)' or 'c.fun(a, b)'?

Also think of autocompletion for 'var x = new' to 'var x = new ByteArenaFactory()', the way you get from nothing to 'ByteArenaFactory' is the same way you get from nothing to '(fun a b c)'.