Dedicated exceptions for read failures reduce the risk of mixing up "user" exceptions with those of Future itself. The risk still exists, if the user allows a chronos exception to bubble up explicitly.
Because await structurally guarantees that the Future is not pending at the time of read, it does not raise this new exception.
introduce FuturePendingError and FutureCompletedError when read:ing a future of uncertain state
introduce pollFor which finishes a Future without reading it, mirroring awaitne
fix waitFor / read to return lent values
simplify code generation for void-returning async procs
Dedicated exceptions for
readfailures reduce the risk of mixing up "user" exceptions with those of Future itself. The risk still exists, if the user allows a chronos exception to bubble up explicitly.Because
awaitstructurally guarantees that the Future is notpendingat the time ofread, it does not raise this new exception.FuturePendingErrorandFutureCompletedErrorwhenread:ing a future of uncertain stateintroducepollForwhich finishes aFuturewithout reading it, mirroringawaitnewaitFor/readto returnlentvaluesvoid-returning async procsRaisingtype helper