convoluted.lua

local mt
local sidetab = {}
mt = {
  __index = function(self,k)
    local l = rawget(mt,k)
    if l then return l end
    return sidetab[self] and sidetab[self][k] or nil
  end,
  __newindex = function(self,k,v)
    local t = sidetab[self] or {}
    t[k] = v
    sidetab[self] = t
  end
}
setmetatable(sidetab, {__mode="k"})

-- this can be c function as well
function mt:method()
  print('hello')
end

-------
l=newproxy()
debug.setmetatable(l,mt)
l:method()
l.x = 1

l2=newproxy()
debug.setmetatable(l2,mt)
l2.x = 2

print(l.x)
print(l2.x)