Struct std::panic::AssertUnwindSafe1.9.0[][src]

pub struct AssertUnwindSafe<T>(pub T);

A simple wrapper around a type to assert that it is unwind safe.

When using catch_unwind it may be the case that some of the closed over variables are not unwind safe. For example if &mut T is captured the compiler will generate a warning indicating that it is not unwind safe. It may not be the case, however, that this is actually a problem due to the specific usage of catch_unwind if unwind safety is specifically taken into account. This wrapper struct is useful for a quick and lightweight annotation that a variable is indeed unwind safe.

Examples

One way to use AssertUnwindSafe is to assert that the entire closure itself is unwind safe, bypassing all checks for all variables:

use std::panic::{self, AssertUnwindSafe};

let mut variable = 4;

// This code will not compile because the closure captures `&mut variable`
// which is not considered unwind safe by default.

// panic::catch_unwind(|| {
//     variable += 3;
// });

// This, however, will compile due to the `AssertUnwindSafe` wrapper
let result = panic::catch_unwind(AssertUnwindSafe(|| {
    variable += 3;
}));
// ...
Run

Wrapping the entire closure amounts to a blanket assertion that all captured variables are unwind safe. This has the downside that if new captures are added in the future, they will also be considered unwind safe. Therefore, you may prefer to just wrap individual captures, as shown below. This is more annotation, but it ensures that if a new capture is added which is not unwind safe, you will get a compilation error at that time, which will allow you to consider whether that new capture in fact represent a bug or not.

use std::panic::{self, AssertUnwindSafe};

let mut variable = 4;
let other_capture = 3;

let result = {
    let mut wrapper = AssertUnwindSafe(&mut variable);
    panic::catch_unwind(move || {
        **wrapper += other_capture;
    })
};
// ...
Run

Trait Implementations

impl<T: Debug> Debug for AssertUnwindSafe<T>1.16.0[src]

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

Formats the value using the given formatter. Read more

impl<T> Deref for AssertUnwindSafe<T>[src]

type Target = T

The resulting type after dereferencing.

fn deref(&self) -> &T

Notable traits for &'_ mut I

impl<'_, I> Iterator for &'_ mut I where
    I: Iterator + ?Sized
type Item = <I as Iterator>::Item;impl<'_, F> Future for &'_ mut F where
    F: Future + Unpin + ?Sized
type Output = <F as Future>::Output;impl<R: Read + ?Sized> Read for &mut Rimpl<W: Write + ?Sized> Write for &mut W
[src]

Dereferences the value.

impl<T> DerefMut for AssertUnwindSafe<T>[src]

fn deref_mut(&mut self) -> &mut T

Notable traits for &'_ mut I

impl<'_, I> Iterator for &'_ mut I where
    I: Iterator + ?Sized
type Item = <I as Iterator>::Item;impl<'_, F> Future for &'_ mut F where
    F: Future + Unpin + ?Sized
type Output = <F as Future>::Output;impl<R: Read + ?Sized> Read for &mut Rimpl<W: Write + ?Sized> Write for &mut W
[src]

Mutably dereferences the value.

impl<R, F: FnOnce() -> R> FnOnce() for AssertUnwindSafe<F>[src]

type Output = R

The returned type after the call operator is used.

extern "rust-call" fn call_once(self, _args: ()) -> R[src]

🔬 This is a nightly-only experimental API. (fn_traits #29625)

Performs the call operation.

impl<F: Future> Future for AssertUnwindSafe<F>1.36.0[src]

type Output = F::Output

The type of value produced on completion.

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

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

impl<S: Stream> Stream for AssertUnwindSafe<S>[src]

type Item = S::Item

🔬 This is a nightly-only experimental API. (async_stream #79024)

The type of items yielded by the stream.

fn poll_next(
    self: Pin<&mut Self>,
    cx: &mut Context<'_>
) -> Poll<Option<S::Item>>
[src]

🔬 This is a nightly-only experimental API. (async_stream #79024)

Attempt to pull out the next value of this stream, registering the current task for wakeup if the value is not yet available, and returning None if the stream is exhausted. Read more

fn size_hint(&self) -> (usize, Option<usize>)[src]

🔬 This is a nightly-only experimental API. (async_stream #79024)

Returns the bounds on the remaining length of the stream. Read more

impl<T> RefUnwindSafe for AssertUnwindSafe<T>[src]

impl<T> UnwindSafe for AssertUnwindSafe<T>[src]

Auto Trait Implementations

impl<T> Send for AssertUnwindSafe<T> where
    T: Send

impl<T> Sync for AssertUnwindSafe<T> where
    T: Sync

impl<T> Unpin for AssertUnwindSafe<T> where
    T: Unpin

Blanket Implementations

impl<T> Any for T where
    T: 'static + ?Sized
[src]

pub fn type_id(&self) -> TypeId[src]

Gets the TypeId of self. Read more

impl<T> Borrow<T> for T where
    T: ?Sized
[src]

pub fn borrow(&self) -> &T

Notable traits for &'_ mut I

impl<'_, I> Iterator for &'_ mut I where
    I: Iterator + ?Sized
type Item = <I as Iterator>::Item;impl<'_, F> Future for &'_ mut F where
    F: Future + Unpin + ?Sized
type Output = <F as Future>::Output;impl<R: Read + ?Sized> Read for &mut Rimpl<W: Write + ?Sized> Write for &mut W
[src]

Immutably borrows from an owned value. Read more

impl<T> BorrowMut<T> for T where
    T: ?Sized
[src]

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

Notable traits for &'_ mut I

impl<'_, I> Iterator for &'_ mut I where
    I: Iterator + ?Sized
type Item = <I as Iterator>::Item;impl<'_, F> Future for &'_ mut F where
    F: Future + Unpin + ?Sized
type Output = <F as Future>::Output;impl<R: Read + ?Sized> Read for &mut Rimpl<W: Write + ?Sized> Write for &mut W
[src]

Mutably borrows from an owned value. Read more

impl<T> From<T> for T[src]

pub fn from(t: T) -> T[src]

Performs the conversion.

impl<T, U> Into<U> for T where
    U: From<T>, 
[src]

pub fn into(self) -> U[src]

Performs the conversion.

impl<F> IntoFuture for F where
    F: Future
[src]

type Output = <F as Future>::Output

🔬 This is a nightly-only experimental API. (into_future #67644)

The output that the future will produce on completion.

type Future = F

🔬 This is a nightly-only experimental API. (into_future #67644)

Which kind of future are we turning this into?

pub fn into_future(self) -> <F as IntoFuture>::Future[src]

🔬 This is a nightly-only experimental API. (into_future #67644)

Creates a future from a value.

impl<T, U> TryFrom<U> for T where
    U: Into<T>, 
[src]

type Error = Infallible

The type returned in the event of a conversion error.

pub fn try_from(value: U) -> Result<T, <T as TryFrom<U>>::Error>[src]

Performs the conversion.

impl<T, U> TryInto<U> for T where
    U: TryFrom<T>, 
[src]

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

The type returned in the event of a conversion error.

pub fn try_into(self) -> Result<U, <U as TryFrom<T>>::Error>[src]

Performs the conversion.