RAII metamethod magic

[stefanos82]

In one of our previous discussions that inspired you to implement Lua's <close> in Nelua, made me think about it even further.

Here's how your original raii.nelua example looks like, with some print()s for debugging:

require 'allocators.general'
require 'string'

local Object: type = @record{ x: integer, y: integer }

function Object:__close()
  print(string.format('object %p destroyed', self))
  general_allocator:delete(self)
end

do
  local o: *Object <close> = general_allocator:new(@Object)

  print(string.format('object %p created', o))
  print(string.format("o.x initial value: %3d, address: %p", o.x, &o.x))
  print(string.format("o.y initial value: %3d, address: %p", o.y, &o.y))

  o.x = 10

  print(string.format("    o.x new value: %3d, address: %p", o.x, &o.x))
end

What I have had in mind for a couple of days now is the following code that looks closer to C++'s RAII than the example above:

local Object: type = @record{}

function Object:__create()
  general_allocator:new(self)
end

function Object:__close()
  general_allocator:delete(self)
end

function Object:__raii()
  self.__create()
  self.__close()
end

do
  local o: *Object <raii> = @Object
end

Assuming Nelua supports these two new metamethods, do you think it's something that could simplify code even further?