Class

local overloaded

function new(Class)
    Class = {}
    Class.__index = Class

    setmetatable(Class, {
        __call = function (cls, ...)
            return cls.new(...)
        end,
    })

    Class.new = overloaded()

    function Class.new.default()
        local self = setmetatable({}, Class)
        return self
    end

    return Class
end

function overloaded()
    local fns = {}
    local mt = {}

    local function oerror()
        return error("Invalid argument types to overloaded function")
    end

    function mt:__call(...)
        local argv = {...}
        local default = self.default

        local signature = {}
            for i,arg in ipairs {...} do
            signature[i] = type(arg)
        end

        signature = table.concat(signature, ",")

        return (fns[signature] or self.default)(...)
    end

    function mt:__index(key)
        local signature = {}
        local function __newindex(self, key, value)
            signature[#signature+1] = key
            fns[table.concat(signature, ",")] = value
        end
        local function __index(self, key)
            signature[#signature+1] = key
            return setmetatable({}, { __index = __index, __newindex = __newindex })
        end
        return __index(self, key)
    end

    function mt:__newindex(key, value)
        fns[key] = value
    end

    return setmetatable({ default = oerror }, mt)
end