This program demonstrates a race condition in the Futures 0.1.19 MPSC
implementation. If a try_send() occurs concurrently with the
Receiver close/drop, a successful send may be indicated even though
the item is actually stuck in a disconnected channel (until the Sender
is dropped).
This program continually tries to recreate this race condition in a
hostile scenario where a busy-polled future polls the MPSC channel a
number of times before disconnecting, while an external thread
busy-loops over sends. The errant condition is detected by observing
that the previously submitted item is still allocated when the Sender
indicates the channel has been disconnected. When this occurs, the
program will output a line similar to the following before exiting:
RACE CONDITION DETECTED on test iteration 465 after 115 send attempts (7 successful).