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

pub struct AssertUnwindSafe<T>(pub T);
Expand description

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

Formats the value using the given formatter. Read more

The resulting type after dereferencing.

Dereferences the value.

Mutably dereferences the value.

The returned type after the call operator is used.

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

Performs the call operation.

The type of value produced on completion.

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

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

The type of items yielded by the stream.

🔬 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

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

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

Auto Trait Implementations

Blanket Implementations

Gets the TypeId of self. Read more

Immutably borrows from an owned value. Read more

Mutably borrows from an owned value. Read more

Performs the conversion.

Performs the conversion.

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

The output that the future will produce on completion.

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

Which kind of future are we turning this into?

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

Creates a future from a value.

The type returned in the event of a conversion error.

Performs the conversion.

The type returned in the event of a conversion error.

Performs the conversion.