@Udiknedormin: I meant right now, since VTable are not available of course.
@monster: It is not safe as is, you must ensure your chain of Msg and MsgBase
pointers have the same lifetime (by putting them in a seq for example).
Otherwise if they are created in different functions, the previous MsgBase
would not exist anymore.
Using concepts, doesn't work yet though because no VTable.
type
QueueID* = distinct uint16
MsgBase* = concept x
x.previous is ptr[MsgBase]
x.sender is QueueID
x.receiver is QueueID
Msg*[T: not (ref|string|seq)] = object
previous: ptr[MsgBase]
sender: QueueID
receiver: QueueID
content*: T
proc initMsg[T](previous: ptr[MsgBase], sender, receiver: QueueID, content:
T): Msg[T] =
result.previous = previous
result.sender = sender
result.receiver = receiver
result.content = content
let a = initMsg(nil, 1.QueueID, 2.QueueID, 42)
echo a # Error: cannot instantiate: 'MsgBase'
