test case or recv-evt problem

[mflatt]

This test is failing on Racket CS (racket/racket#3457):

 (test-case
    "An evt-set syncs to the list of results of evts."
    (define πs (for/list ([i 10]) (process (λ () (emit i)))))
    (define evt (apply evt-set (map recv-evt πs)))
    (check equal? (sync evt) '(0 1 2 3 4 5 6 7 8 9)))

It looks like recv-evt uses the same channel to receive all events in a given process. So, even if the third recv-evt becomes ready, it doesn't necessarily receive a value from the third element of πs; it might pick up the value from the fifth element of πs, while some other recv-evt gets the result of the third element of πs. Put another way, changing recv-evt to use (make-exchanger) in place of (process-rx (current-process)) causes the test to pass — but I don't know whether it's rect-evt or the test that should be considered wrong, or if I'm missing something else.