var myPendingRequests {.threadvar.}: HashSet[ptr MsgBase]
myPendingRequests.init()
The compiler made you write this, it disallows `var myPendingRequests
{.threadvar.} = initSet[ptr MsgBase]()`. Ever wondered why? Because it would
only run for the main thread. I improved its error message in the hope it
clears things up.
