completionVar in Network.Mux

[coot]

The completionVar :: TMVar m (Either SomeException a) can be simplified to TMVar m a.

[dcoutts]

I'd go the other way and eliminate the muxStatus TVar. Instead, the job pool shutdown can fill in the completion var for each thread with the exception that terminated the mux. Or for the case of a specific protocol thread that raised an exception, its completion var can be filled in with that specific exception.