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.


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;
// ...

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;
// ...

Trait Implementations

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

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

type Target = T

The resulting type after dereferencing.

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

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

type Output = R

The returned type after the call operator is used.

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

type Output = F::Output

The type of value produced on completion.

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

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.

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

impl<T> Borrow<T> for T where
    T: ?Sized

impl<T> BorrowMut<T> for T where
    T: ?Sized

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

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

impl<F> IntoFuture for F where
    F: Future

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?

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

type Error = Infallible

The type returned in the event of a conversion error.

impl<T, U> TryInto<U> for T where
    U: TryFrom<T>, 

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

The type returned in the event of a conversion error.