On Mon, 23 Oct 2017 23:05:42 GMT, Sönke Ludwig wrote: 

void fn(const Task task)
{
    ...
    taskIdToStore = task.tid.toString;
    ....
}

and can't because of 'mutable method vibe.core.task.Task.tid is not callable using a const object'

The method itself can be made inout, but the problem is that, AFAICS, a const(Tid) isn't usable for sending or receiving messages either.

Yes, I understand. But it still can be useful if I want only to collect tasks ID's to use it in another place.