Why no syntax sugar for function object?

[Dirk Laurie <dirk.laurie@...>]

I can't say:
  for x in f = object:method do

Instead, I must say
  for f in function(...) return object:method(...) end do

The error seems to be at syntax level:

stdin:1: function arguments expected near 'do'

Is there some philosophical reason why this sugar is not available?