Hi!
I need to send Publish struct from
https://github.com/tchaloupka/vibe-mqtt to another vibe.d task.
And there is the problem. First of all, I can't make it immutable
because send() wants to mutate it. I can't send local copy
because of "Aliases to mutable thread-local data not allowed.".
And I can't convert it to shared because of "cannot implicitly
convert expression `packet` of type `Publish` to
`shared(FixedHeader)`".
I don't understand error message about FixedHeader. Why it tries
to convert struct to its field? As I understand the real problem
here is `ubyte[] payload` dynamic array field in Publish which is
allocated separately, so to make a shared copy of Publish it need
the deep copy of this struct. How to do it right? I don't want to
copy all fields manually, is there a standard way to accomplish
it?
```
struct MqttOnPublish
{
Publish packet;
}
override void onPublish(Publish packet)
{
super.onPublish(packet);
// source/vcm/mqtt/bridge.d(69,41): Error: cannot implicitly
convert expression `packet` of type `Publish` to
`shared(FixedHeader)`
shared Publish sp = shared Publish(packet);
/* /usr/include/dmd/phobos/std/concurrency.d(575,5): Error:
static assert "Aliases to mutable thread-local data not allowed."
../../.dub/packages/vibe-d-0.8.1/vibe-d/core/vibe/core/concurrency.d(1243,64):
instantiated from here: send!(MqttOnPublish)
source/vision/eventbus.d(72,27): instantiated from here:
send!(MqttOnPublish)
source/vision/eventbus.d(42,13): instantiated from here:
emit!(MqttOnPublish)
source/vcm/mqtt/bridge.d(70,14): instantiated from here:
emit!(MqttOnPublish)
*/
bus.emit(MqttOnPublish(packet));
}
```