Struct Task 

pub struct Task<I: TaskImpl>(/* private fields */);

A wrapper around implementation-specific tasks that implement the TaskImpl trait

Awaiting a Task yields the task’s output. That output type leaves no room to report a failure, so on the backends which can detect one — tokio, smol and async-global-executor — a task which panicked resumes its panic in the awaiting task, and awaiting one which was canceled, or whose runtime went away, panics too. Noop is the exception: it runs nothing, and its tasks simply never complete.

Note that cancel takes &mut self, so awaiting a Task after canceling it is expressible and panics rather than failing to compile. The same goes for a cancel which was itself dropped before it completed — in a select!, or a TryJoin which short-circuited: it has already given up the underlying task by then, so the Task is spent even though no cancellation result was ever handed back.

Implementations

impl<I: TaskImpl> Task<I>

pub async fn cancel(&mut self) -> Option<<Self as Future>::Output>

Cancel the task, returning data if it was already finished

This gives up the underlying task, so the Task has nothing left to wait for: see the type-level docs for what awaiting it afterwards does.

None means the task did not complete, and does not say why: one which panicked comes back as None here rather than resuming its panic the way awaiting it would. The output type has no room to tell the two apart, on any of the backends.

Trait Implementations

impl<I: Debug + TaskImpl> Debug for Task<I>

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl<I: TaskImpl> Drop for Task<I>

fn drop(&mut self)

Executes the destructor for this type.

fn pin_drop(self: Pin<&mut Self>)

🔬This is a nightly-only experimental API. (pin_ergonomics)

Execute the destructor for this type, but different to Drop::drop, it requires self to be pinned.

impl<I: TaskImpl> From<I> for Task<I>

fn from(task_impl: I) -> Self

Converts to this type from the input type.

impl<I: TaskImpl> Future for Task<I>

type Output = <I as Future>::Output

The type of value produced on completion.

fn poll(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Self::Output>

Attempts to resolve the future to a final value, registering the current task for wakeup if the value is not yet available.