ContextBuilder in core::task - Rust
Description: A Builder used to construct a `Context` instance with support for `LocalWaker`.

# Struct ContextBuilder

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    pub struct ContextBuilder<'a> { /* private fields */ }

🔬This is a nightly-only experimental API. (`local_waker` #118959)
Expand description

A Builder used to construct a `Context` instance with support for `LocalWaker`.

## §Examples

    #![feature(local_waker)]
    use std::task::{ContextBuilder, LocalWaker, Waker, Poll};
    use std::future::Future;

    let local_waker = LocalWaker::noop();
    let waker = Waker::noop();

    let mut cx = ContextBuilder::from_waker(&waker)
        .local_waker(&local_waker)
        .build();

    let mut future = std::pin::pin!(async { 20 });
    let poll = future.as_mut().poll(&mut cx);
    assert_eq!(poll, Poll::Ready(20));

## Implementations§

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### impl<'a> ContextBuilder<'a>

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#### pub const fn from_waker(waker: &'a Waker) -> Self

🔬This is a nightly-only experimental API. (`local_waker` #118959)

Creates a ContextBuilder from a Waker.

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#### pub const fn from(cx: &'a mut Context<'_>) -> Self

🔬This is a nightly-only experimental API. (`context_ext` #123392)

Creates a ContextBuilder from an existing Context.

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#### pub const fn waker(self, waker: &'a Waker) -> Self

🔬This is a nightly-only experimental API. (`context_ext` #123392)

Sets the value for the waker on `Context`.

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#### pub const fn local_waker(self, local_waker: &'a LocalWaker) -> Self

🔬This is a nightly-only experimental API. (`local_waker` #118959)

Sets the value for the local waker on `Context`.

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#### pub const fn ext(self, data: &'a mut dyn Any) -> Self

🔬This is a nightly-only experimental API. (`context_ext` #123392)

Sets the value for the extension data on `Context`.

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#### pub const fn build(self) -> Context<'a>

🔬This is a nightly-only experimental API. (`local_waker` #118959)

Builds the `Context`.

## Trait Implementations§

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### impl<'a> Debug for ContextBuilder<'a>

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

Formats the value using the given formatter. Read more

## Auto Trait Implementations§

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### impl<'a> Freeze for ContextBuilder<'a>

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### impl<'a> !RefUnwindSafe for ContextBuilder<'a>

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### impl<'a> !Send for ContextBuilder<'a>

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### impl<'a> !Sync for ContextBuilder<'a>

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### impl<'a> Unpin for ContextBuilder<'a>

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### impl<'a> !UnwindSafe for ContextBuilder<'a>

## Blanket Implementations§

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### impl<T> Any for T
where T: 'static + ?Sized,

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#### fn type_id(&self) -> TypeId

Gets the `TypeId` of `self`. Read more
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### impl<T> Borrow<T> for T
where T: ?Sized,

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#### fn borrow(&self) -> &T

Immutably borrows from an owned value. Read more
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### impl<T> BorrowMut<T> for T
where T: ?Sized,

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#### fn borrow_mut(&mut self) -> &mut T

Mutably borrows from an owned value. Read more
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### impl<T> From<T> for T

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#### fn from(t: T) -> T

Returns the argument unchanged.

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### impl<T, U> Into<U> for T
where U: From<T>,

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#### fn into(self) -> U

Calls `U::from(self)`.

That is, this conversion is whatever the implementation of `From<T> for U` chooses to do.

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### impl<T, U> TryFrom<U> for T
where U: Into<T>,

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#### type Error = Infallible

The type returned in the event of a conversion error.
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#### fn try_from(value: U) -> Result<T, <T as TryFrom<U>>::Error>

Performs the conversion.
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### impl<T, U> TryInto<U> for T
where U: TryFrom<T>,

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#### type Error = <U as TryFrom<T>>::Error

The type returned in the event of a conversion error.
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#### fn try_into(self) -> Result<U, <U as TryFrom<T>>::Error>

Performs the conversion.