In the "ttl tasks" loop of the fifottl and utubettl driver fibers the loop variable shadows the state module:

Inside the loop state is a status string, so state.DONE indexes a string and evaluates to nil. transform(2, 1, nil) then writes NULL into the status field instead of DONE:

tarantool> box.tuple.new{10, 'r', 111}:transform(2, 1, nil)
---
- [10, null, 111]
...

So the task passed to the user's on_task_change callback with the ttl event is malformed. Internal bookkeeping is unaffected: the READY/TAKEN branches in abstract.lua are skipped for a deleted task anyway and the statistics are still counted.

Steps to reproduce

local tube = queue.create_tube('t', 'fifottl', {ttl = 0.1,
    on_task_change = function(task, event)
        if event == 'ttl' then require('log').info('status: %s', tostring(task[2])) end
    end})
tube:put('expired')

Actual behavior

status: cdata<void *>: NULL

Expected behavior

status: - (state.DONE)

Renaming the loop variable is enough.