Newtype wrapper around ValueOverlay<PythonResponseMessage> needed
because PythonMessageKind is a #[pyclass] enum, requiring all variant
fields to implement PyO3 traits. ValueOverlay is defined in another crate
and does not implement PyClass.
Truthy while any callback is waiting on _callback_loop.
_dispatch_loop yields to the event loop between messages while this is
true: recv does not yield when a message is already queued, so a
backlog of messages would otherwise starve _callback_loop.
A port that drops all messages sent to it.
Used when there is no response port for a message.
Any exceptions sent to it are re-raised in the current actor.
A supervision event enqueued for _callback_loop, or for a sync actor’s
driver, which runs __supervise__ and reports the verdict with _handled
or _raised.
Dropping it without reporting (for example because an async loop was
cancelled, sync cleanup won the claim, or the inbox was dropped) produces no
verdict.
An undeliverable message enqueued for _callback_loop, or for a sync
actor’s driver, which runs _handle_undeliverable_message and reports the
verdict with _handled or _raised. Dropping it without reporting (for
example because an async loop was cancelled, sync cleanup won the claim, or
the inbox was dropped) produces no verdict.
Whether a Python actor is sync (it declares at least one endpoint, and every
endpoint is a plain def) or async. Python’s _actor_kind decides it for a
class spawned on a ProcMesh; every other construction route states it
(SA-5, defined in monarch._src.actor.actor_mesh).