-- Example self-implementation
local old_type = type

function type(object)
    if old_type(object) ~= "table" then
	return old_type(object)
    else
	local mt = getmetatable(object)

	if old_type(mt) == "table" then
	    if old_type(mt.__type) == "function" then
		return mt.__type(object)
	    else
		return mt.__type
	    end
	else
	    return "table"
	end
    end
end

-- This will work
local ok_table = {
    __type = "OK table"
}

setmetatable(ok_table, ok_table)

print(type(ok_table))
-- > OK table

-- This will *not* work; setting __metatable blocks our new
-- type() function from working
local bad_table = {
    __type = "Bad table"
    __metatable = "No can has"
}

setmetatable(bad_table, bad_table)

print(type(bad_table))
-- > table (in this case)