Discard {main} suspension on uncaught exception from loop

[trowski]

If an exception is thrown from the event loop, the suspension for {main} will throw "Must call suspend() before calling resume()" because the suspension has been marked as no longer pending before throwing the exception from the loop.

event-loop/src/EventLoop/Internal/DriverSuspension.php

Lines 101 to 102 in 81dd825

	$this->pending = false;
	$result && $result(); // Unwrap any uncaught exceptions from the event loop

This PR retains that suspension in the instance of DriverSuspension and rethrows the exception from any call to resume() or throw() in the same way as we were already throwing a FiberError.

This new behavior only affects shutdown after an uncaught exception from the event loop and {main} has not been suspended again, which prior to this change was throwing an Error, but now will throw UncaughtThrowable.

[Bilge]

This new behavior only effects

ahem. Hate to be that guy, but... affects.

Actually, I love to be that guy.

[kelunik]

This new behavior only affects shutdown after an uncaught exception from the event loop and {main} has not been suspended again, which prior to this change was throwing an Error, but now will throw UncaughtThrowable.

No, this affects everything throwing exceptions and using suspensions, because the reference is now retained and cannot be garbage collected, which is even more problematic with exceptions keeping a reference to arguments in the stack trace.

[trowski]

Not everything throwing exceptions, only those thrown from the event loop. The change is only on the path that would have thrown an Error anyway. Normal throwing of exceptions is unaffected.

[trowski]

@kelunik Could you have another look at this. Instead of retaining the uncaught exception from the event loop, another Error instances is created and thrown instead. The cached suspension for {main} is discarded when throwing from the event loop, allowing the event loop to be re-entered from a shutdown function, while keeping the prior suspension invalid in case it is resumed.