Constant ZX_ERR_ASYNC 

pub const ZX_ERR_ASYNC: i32 = -62;

Ownership of the item has moved to an asynchronous worker.

The flow control values ZX_ERR_STOP, ZX_ERR_NEXT, and ZX_ERR_ASYNC are not errors and will never be returned by a system call or public API. They allow callbacks to request their caller perform some other operation.

Unlike ZX_ERR_STOP, which implies that iteration on an object should stop, and ZX_ERR_NEXT, which implies that iteration should continue to the next item, ZX_ERR_ASYNC implies that an asynchronous worker is responsible for continuing iteration.

For example, a callback will be called on every event, but one event needs to handle some work asynchronously before it can continue. ZX_ERR_ASYNC implies the worker is responsible for resuming iteration once its work has completed.