init after completed

[JanKoelzer]

cell1 = pool.createCell(new DefaultKey[Int], () => {
// depend on a already completed cell, callback is triggered immediately
cell1.whenComplete(completed, _ => FinalOutcome(10))

cell1.onComplete(_ => latch.countDown())
latch.await() // meanwhile, cell1 gets final value 10 via whenComplete

NextOutcome(-1) // the intended initial value of cell1.
})

If the PR on lazy evaluation gets accepted, simply catch the exception that is thrown when init() is called and the returned value is put.

[JanKoelzer]

Most simple solution is to catch the exception in HandlerPool.triggerExecution(). BUT: Double check, if this could lead to different outputs (value vs. exception) depending on the order of execution. In particular check this for values that are compatible and for values that are incompatible. In the first case, init() could return both the lower and also the greater value in lattice order.

[JanKoelzer]

Catching the exception now. PR to upstream includes this.

[JanKoelzer]

Check, if LatticeViolationExceptions are handled correctly. (I guess, that in both orders of execution an exception should be passed to the exception handler)

[JanKoelzer]

Latest version does not catch the exception. LatticeViolationExceptions should all be thrown (phaller) and to not violate quasi-determinism.
Instead,we decieded to stall whenNext/whenComplete while in init. This avoids the exceptions.