caching anonymous closures called in-place in 5.2

[David Manura <dm.lua@...>]

In order for the following code to cache closures in 5.2.0-work4,

  for i=1,1000 do
    print((function()
      if i % 2 == 0 then return false else return i end
    end)())
  end

it currently needs to be rewritten as

  for i=1,1000 do
    print((function(i)
      if i % 2 == 0 then return false else return i end
    end)(i))
  end

Couldn't it cache this case without rewriting?  Defining an anonymous
function and then immediately calling it (once) is a common pattern
for doing statements inside expressions.  The lifetime of such a
function does not extend beyond that normal lifetime of its variables,
so it's not really used as a closure.  That is true unless you did
something odd with the debug library to grab the currently running
function and store it away somewhere for later use.