# tokio::task::JoinError - Rust
API documentation for the Rust `JoinError` struct in crate `tokio`.
Keywords: rust, rustlang, rust-lang, JoinError

# Struct tokio::task::JoinError [−] [src]

    pub struct JoinError { /* fields omitted */ }

Task failed to execute to completion.

## Implementations

### `impl JoinError` [src]

#### `pub fn is_cancelled(&self) -> bool` [src]

Returns true if the error was caused by the task being cancelled

#### `pub fn is_panic(&self) -> bool` [src]

Returns true if the error was caused by the task panicking

# Examples

    use std::panic;

    #[tokio::main]
    async fn main() {
        let err = tokio::spawn(async {
            panic!("boom");
        }).await.unwrap_err();

        assert!(err.is_panic());
    }

#### `pub fn into_panic(self) -> Box<dyn Any + Send + 'static>ⓘ

### Notable traits for Box<F, A>

`impl<F, A> Future for Box<F, A> where
F: Unpin + Future + ?Sized,
A: Allocator + 'static, type Output = <F as Future>::Output;`
` [src]

Consumes the join error, returning the object with which the task panicked.

# Panics

`into_panic()` panics if the `Error` does not represent the underlying task terminating with a panic. Use `is_panic` to check the error reason or `try_into_panic` for a variant that does not panic.

# Examples

ⓘ

    use std::panic;

    #[tokio::main]
    async fn main() {
        let err = tokio::spawn(async {
            panic!("boom");
        }).await.unwrap_err();

        if err.is_panic() {
            // Resume the panic on the main task
            panic::resume_unwind(err.into_panic());
        }
    }

#### `pub fn try_into_panic(self) -> Result<Box<dyn Any + Send + 'static>, JoinError>` [src]

Consumes the join error, returning the object with which the task panicked if the task terminated due to a panic. Otherwise, `self` is returned.

# Examples

ⓘ

    use std::panic;

    #[tokio::main]
    async fn main() {
        let err = tokio::spawn(async {
            panic!("boom");
        }).await.unwrap_err();

        if let Ok(reason) = err.try_into_panic() {
            // Resume the panic on the main task
            panic::resume_unwind(reason);
        }
    }

## Trait Implementations

### `impl Debug for JoinError` [src]

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

Formats the value using the given formatter. Read more

### `impl Display for JoinError` [src]

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

Formats the value using the given formatter. Read more

### `impl Error for JoinError` [src]

#### `pub fn source(&self) -> Option<&(dyn Error + 'static)>`1.30.0 [src]

The lower-level source of this error, if any. Read more

#### `pub fn backtrace(&self) -> Option<&Backtrace>` [src]

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

Returns a stack backtrace, if available, of where this error occurred. Read more

#### `pub fn description(&self) -> &str` 1.0.0 [src]

👎 Deprecated since 1.42.0:

use the Display impl or to_string()

Read more

#### `pub fn cause(&self) -> Option<&dyn Error>`1.0.0 [src]

👎 Deprecated since 1.33.0:

replaced by Error::source, which can support downcasting

## Auto Trait Implementations

### `impl RefUnwindSafe for JoinError` [src]

### `impl Send for JoinError` [src]

### `impl Sync for JoinError` [src]

### `impl Unpin for JoinError` [src]

### `impl UnwindSafe for JoinError` [src]

## 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 F

`impl<'_, F> Future for &'_ mut F where
F: Unpin + Future + ?Sized, type Output = <F as Future>::Output;`
` [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 F

`impl<'_, F> Future for &'_ mut F where
F: Unpin + Future + ?Sized, type Output = <F as Future>::Output;`
` [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<T> ToString for T where
T: Display + ?Sized,` [src]

#### `pub default fn to_string(&self) -> String` [src]

Converts the given value to a `String`. Read more

### `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.