Trait std::error::Error

pub trait Error: Debug + Display {
    fn source(&self) -> Option<&(dyn Error + 'static)> { ... }
    fn backtrace(&self) -> Option<&Backtrace> { ... }
    fn description(&self) -> &str { ... }
    fn cause(&self) -> Option<&dyn Error> { ... }
}

Error 是 trait，表示对错误值 (即 Result<T, E> 中的 E 类型的值) 的基本期望。

错误必须通过 Display 和 Debug traits 来描述自己。 错误消息通常是简洁的小写句子，没有尾随标点符号:

let err = "NaN".parse::<u32>().unwrap_err();
assert_eq!(err.to_string(), "invalid digit found in string");

错误可能会提供原因链信息。Error::source() 通常在错误交叉 “abstraction boundaries” 时使用。 如果一个模块必须报告由下级模块的错误引起的错误，则它可以允许通过 Error::source() 访问该错误。 这使得高级模块可以提供自己的错误，同时还可以公开一些通过 source 链进行调试的实现。

Provided methods

fn source(&self) -> Option<&(dyn Error + 'static)>

此错误的下级来源 (如果有)。

Examples

use std::error::Error;
use std::fmt;

#[derive(Debug)]
struct SuperError {
    side: SuperErrorSideKick,
}

impl fmt::Display for SuperError {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        write!(f, "SuperError is here!")
    }
}

impl Error for SuperError {
    fn source(&self) -> Option<&(dyn Error + 'static)> {
        Some(&self.side)
    }
}

#[derive(Debug)]
struct SuperErrorSideKick;

impl fmt::Display for SuperErrorSideKick {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        write!(f, "SuperErrorSideKick is here!")
    }
}

impl Error for SuperErrorSideKick {}

fn get_super_error() -> Result<(), SuperError> {
    Err(SuperError { side: SuperErrorSideKick })
}

fn main() {
    match get_super_error() {
        Err(e) => {
            println!("Error: {}", e);
            println!("Caused by: {}", e.source().unwrap());
        }
        _ => println!("No error"),
    }
}

fn backtrace(&self) -> Option<&Backtrace>

🔬 This is a nightly-only experimental API. (backtrace #53487)

返回发生错误的栈回溯 (如果有)。

该函数允许检查代码中发生错误的位置。 返回的 Backtrace 包含有关执行错误来源的 OS 线程的栈跟踪的信息。

请注意，并非所有错误都包含 Backtrace。另请注意，Backtrace 实际上可能为空。 有关更多信息，请查阅 Backtrace 类型本身。

fn description(&self) -> &str

👎 Deprecated since 1.42.0:

use the Display impl or to_string()

if let Err(e) = "xc".parse::<u32>() {
    // 打印 `e` 本身，不需要 description()。
    eprintln!("Error: {}", e);
}

fn cause(&self) -> Option<&dyn Error>

👎 Deprecated since 1.33.0:

replaced by Error::source, which can support downcasting

Implementations

impl dyn Error + 'static

pub fn is<T: Error + 'static>(&self) -> bool

如果 boxed 类型与 T 相同，则返回 true

pub fn downcast_ref<T: Error + 'static>(&self) -> Option<&T>

如果 boxed 的类型为 T，则返回一些引用，如果不是，则返回 None。

pub fn downcast_mut<T: Error + 'static>(&mut self) -> Option<&mut T>

如果 boxed 的类型为 T，则返回一些可变引用; 如果不是，则返回 None。

impl dyn Error + Send + 'static

pub fn is<T: Error + 'static>(&self) -> bool

转发到在 dyn Error 类型上定义的方法。

pub fn downcast_ref<T: Error + 'static>(&self) -> Option<&T>

转发到在 dyn Error 类型上定义的方法。

pub fn downcast_mut<T: Error + 'static>(&mut self) -> Option<&mut T>

转发到在 dyn Error 类型上定义的方法。

impl dyn Error + Send + Sync + 'static

pub fn is<T: Error + 'static>(&self) -> bool

转发到在 dyn Error 类型上定义的方法。

pub fn downcast_ref<T: Error + 'static>(&self) -> Option<&T>

转发到在 dyn Error 类型上定义的方法。

pub fn downcast_mut<T: Error + 'static>(&mut self) -> Option<&mut T>

转发到在 dyn Error 类型上定义的方法。

impl dyn Error

pub fn downcast<T: Error + 'static>(
    self: Box<Self>
) -> Result<Box<T>, Box<dyn Error>>

尝试将 box 转换为具体类型。

pub fn chain(&self) -> Chain<'_>

🔬 This is a nightly-only experimental API. (error_iter #58520)

返回一个迭代器，该迭代器从当前错误开始，然后以递归方式调用 Error::source。

如果要忽略当前错误并仅使用其来源，请使用 skip(1)。

Examples

#![feature(error_iter)]
use std::error::Error;
use std::fmt;

#[derive(Debug)]
struct A;

#[derive(Debug)]
struct B(Option<Box<dyn Error + 'static>>);

impl fmt::Display for A {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        write!(f, "A")
    }
}

impl fmt::Display for B {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        write!(f, "B")
    }
}

impl Error for A {}

impl Error for B {
    fn source(&self) -> Option<&(dyn Error + 'static)> {
        self.0.as_ref().map(|e| e.as_ref())
    }
}

let b = B(Some(Box::new(A)));

// 令 err: Box<Error> = b.into(); // 或者
let err = &b as &(dyn Error);

let mut iter = err.chain();

assert_eq!("B".to_string(), iter.next().unwrap().to_string());
assert_eq!("A".to_string(), iter.next().unwrap().to_string());
assert!(iter.next().is_none());
assert!(iter.next().is_none());

impl dyn Error + Send

pub fn downcast<T: Error + 'static>(
    self: Box<Self>
) -> Result<Box<T>, Box<dyn Error + Send>>

尝试将 box 转换为具体类型。

impl dyn Error + Send + Sync

pub fn downcast<T: Error + 'static>(
    self: Box<Self>
) -> Result<Box<T>, Box<Self>>

尝试将 box 转换为具体类型。

Implementations on Foreign Types

impl Error for FromSecsError

Implementors

impl Error for TryReserveError

impl Error for Infallible

fn description(&self) -> &str

👎 Deprecated since 1.42.0:

use the Display impl or to_string()

impl Error for VarError

fn description(&self) -> &str

👎 Deprecated since 1.42.0:

use the Display impl or to_string()

impl Error for RecvTimeoutError

fn description(&self) -> &str

👎 Deprecated since 1.42.0:

use the Display impl or to_string()

impl Error for TryRecvError

fn description(&self) -> &str

👎 Deprecated since 1.42.0:

use the Display impl or to_string()

impl Error for !

impl Error for AllocError

impl Error for LayoutError

impl Error for TryFromSliceError

fn description(&self) -> &str

👎 Deprecated since 1.42.0:

use the Display impl or to_string()

impl Error for BorrowError

fn description(&self) -> &str

👎 Deprecated since 1.42.0:

use the Display impl or to_string()

impl Error for BorrowMutError

fn description(&self) -> &str

👎 Deprecated since 1.42.0:

use the Display impl or to_string()

impl Error for CharTryFromError

fn description(&self) -> &str

👎 Deprecated since 1.42.0:

use the Display impl or to_string()

impl Error for DecodeUtf16Error

fn description(&self) -> &str

👎 Deprecated since 1.42.0:

use the Display impl or to_string()

impl Error for ParseCharError

fn description(&self) -> &str

👎 Deprecated since 1.42.0:

use the Display impl or to_string()

impl Error for JoinPathsError

fn description(&self) -> &str

👎 Deprecated since 1.42.0:

use the Display impl or to_string()

impl Error for FromBytesWithNulError

fn description(&self) -> &str

👎 Deprecated since 1.42.0:

use the Display impl or to_string()

impl Error for FromVecWithNulError

impl Error for IntoStringError

fn description(&self) -> &str

👎 Deprecated since 1.42.0:

use the Display impl or to_string()

fn source(&self) -> Option<&(dyn Error + 'static)>

impl Error for NulError

fn description(&self) -> &str

👎 Deprecated since 1.42.0:

use the Display impl or to_string()

impl Error for std::fmt::Error

fn description(&self) -> &str

👎 Deprecated since 1.42.0:

use the Display impl or to_string()

impl Error for std::io::Error

fn description(&self) -> &str

👎 Deprecated since 1.42.0:

use the Display impl or to_string()

fn cause(&self) -> Option<&dyn Error>

👎 Deprecated since 1.33.0:

replaced by Error::source, which can support downcasting

fn source(&self) -> Option<&(dyn Error + 'static)>

impl Error for AddrParseError

fn description(&self) -> &str

👎 Deprecated since 1.42.0:

use the Display impl or to_string()

impl Error for ParseFloatError

fn description(&self) -> &str

👎 Deprecated since 1.42.0:

use the Display impl or to_string()

impl Error for ParseIntError

fn description(&self) -> &str

👎 Deprecated since 1.42.0:

use the Display impl or to_string()

impl Error for TryFromIntError

fn description(&self) -> &str

👎 Deprecated since 1.42.0:

use the Display impl or to_string()

impl Error for StripPrefixError

fn description(&self) -> &str

👎 Deprecated since 1.42.0:

use the Display impl or to_string()

impl Error for ExitStatusError

impl Error for ParseBoolError

fn description(&self) -> &str

👎 Deprecated since 1.42.0:

use the Display impl or to_string()

impl Error for Utf8Error

fn description(&self) -> &str

👎 Deprecated since 1.42.0:

use the Display impl or to_string()

impl Error for FromUtf8Error

fn description(&self) -> &str

👎 Deprecated since 1.42.0:

use the Display impl or to_string()

impl Error for FromUtf16Error

fn description(&self) -> &str

👎 Deprecated since 1.42.0:

use the Display impl or to_string()

impl Error for RecvError

fn description(&self) -> &str

👎 Deprecated since 1.42.0:

use the Display impl or to_string()

impl Error for AccessError

impl Error for SystemTimeError

fn description(&self) -> &str

👎 Deprecated since 1.42.0:

use the Display impl or to_string()

impl<'a, K: Debug + Ord, V: Debug> Error for std::collections::btree_map::OccupiedError<'a, K, V>

fn description(&self) -> &str

👎 Deprecated since 1.42.0:

use the Display impl or to_string()

impl<'a, K: Debug, V: Debug> Error for std::collections::hash_map::OccupiedError<'a, K, V>

fn description(&self) -> &str

👎 Deprecated since 1.42.0:

use the Display impl or to_string()

impl<'a, T: Error + ?Sized> Error for &'a T

fn description(&self) -> &str

👎 Deprecated since 1.42.0:

use the Display impl or to_string()

fn cause(&self) -> Option<&dyn Error>

👎 Deprecated since 1.33.0:

replaced by Error::source, which can support downcasting

fn source(&self) -> Option<&(dyn Error + 'static)>

fn backtrace(&self) -> Option<&Backtrace>

🔬 This is a nightly-only experimental API. (backtrace #53487)

impl<T> Error for TryLockError<T>

fn description(&self) -> &str

👎 Deprecated since 1.42.0:

use the Display impl or to_string()

fn cause(&self) -> Option<&dyn Error>

👎 Deprecated since 1.33.0:

replaced by Error::source, which can support downcasting

impl<T> Error for PoisonError<T>

fn description(&self) -> &str

👎 Deprecated since 1.42.0:

use the Display impl or to_string()

impl<T: Send> Error for TrySendError<T>

fn description(&self) -> &str

👎 Deprecated since 1.42.0:

use the Display impl or to_string()

impl<T: Send> Error for SendError<T>

fn description(&self) -> &str

👎 Deprecated since 1.42.0:

use the Display impl or to_string()

impl<T: Error + ?Sized> Error for Arc<T>

fn description(&self) -> &str

👎 Deprecated since 1.42.0:

use the Display impl or to_string()

fn cause(&self) -> Option<&dyn Error>

👎 Deprecated since 1.33.0:

replaced by Error::source, which can support downcasting

fn source(&self) -> Option<&(dyn Error + 'static)>

fn backtrace(&self) -> Option<&Backtrace>

🔬 This is a nightly-only experimental API. (backtrace #53487)

impl<T: Error> Error for Box<T>

fn description(&self) -> &str

👎 Deprecated since 1.42.0:

use the Display impl or to_string()

fn cause(&self) -> Option<&dyn Error>

👎 Deprecated since 1.33.0:

replaced by Error::source, which can support downcasting

fn source(&self) -> Option<&(dyn Error + 'static)>

impl<W: Send + Debug> Error for IntoInnerError<W>

fn description(&self) -> &str

👎 Deprecated since 1.42.0:

use the Display impl or to_string()