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Diffstat (limited to '')
| -rw-r--r-- | library/std/src/error.rs | 1196 |
1 files changed, 13 insertions, 1183 deletions
diff --git a/library/std/src/error.rs b/library/std/src/error.rs index 722df119d..05f8fd8de 100644 --- a/library/std/src/error.rs +++ b/library/std/src/error.rs @@ -1,366 +1,14 @@ -//! Interfaces for working with Errors. -//! -//! # Error Handling In Rust -//! -//! The Rust language provides two complementary systems for constructing / -//! representing, reporting, propagating, reacting to, and discarding errors. -//! These responsibilities are collectively known as "error handling." The -//! components of the first system, the panic runtime and interfaces, are most -//! commonly used to represent bugs that have been detected in your program. The -//! components of the second system, `Result`, the error traits, and user -//! defined types, are used to represent anticipated runtime failure modes of -//! your program. -//! -//! ## The Panic Interfaces -//! -//! The following are the primary interfaces of the panic system and the -//! responsibilities they cover: -//! -//! * [`panic!`] and [`panic_any`] (Constructing, Propagated automatically) -//! * [`PanicInfo`] (Reporting) -//! * [`set_hook`], [`take_hook`], and [`#[panic_handler]`][panic-handler] (Reporting) -//! * [`catch_unwind`] and [`resume_unwind`] (Discarding, Propagating) -//! -//! The following are the primary interfaces of the error system and the -//! responsibilities they cover: -//! -//! * [`Result`] (Propagating, Reacting) -//! * The [`Error`] trait (Reporting) -//! * User defined types (Constructing / Representing) -//! * [`match`] and [`downcast`] (Reacting) -//! * The question mark operator ([`?`]) (Propagating) -//! * The partially stable [`Try`] traits (Propagating, Constructing) -//! * [`Termination`] (Reporting) -//! -//! ## Converting Errors into Panics -//! -//! The panic and error systems are not entirely distinct. Often times errors -//! that are anticipated runtime failures in an API might instead represent bugs -//! to a caller. For these situations the standard library provides APIs for -//! constructing panics with an `Error` as it's source. -//! -//! * [`Result::unwrap`] -//! * [`Result::expect`] -//! -//! These functions are equivalent, they either return the inner value if the -//! `Result` is `Ok` or panic if the `Result` is `Err` printing the inner error -//! as the source. The only difference between them is that with `expect` you -//! provide a panic error message to be printed alongside the source, whereas -//! `unwrap` has a default message indicating only that you unwraped an `Err`. -//! -//! Of the two, `expect` is generally preferred since its `msg` field allows you -//! to convey your intent and assumptions which makes tracking down the source -//! of a panic easier. `unwrap` on the other hand can still be a good fit in -//! situations where you can trivially show that a piece of code will never -//! panic, such as `"127.0.0.1".parse::<std::net::IpAddr>().unwrap()` or early -//! prototyping. -//! -//! # Common Message Styles -//! -//! There are two common styles for how people word `expect` messages. Using -//! the message to present information to users encountering a panic -//! ("expect as error message") or using the message to present information -//! to developers debugging the panic ("expect as precondition"). -//! -//! In the former case the expect message is used to describe the error that -//! has occurred which is considered a bug. Consider the following example: -//! -//! ```should_panic -//! // Read environment variable, panic if it is not present -//! let path = std::env::var("IMPORTANT_PATH").unwrap(); -//! ``` -//! -//! In the "expect as error message" style we would use expect to describe -//! that the environment variable was not set when it should have been: -//! -//! ```should_panic -//! let path = std::env::var("IMPORTANT_PATH") -//! .expect("env variable `IMPORTANT_PATH` is not set"); -//! ``` -//! -//! In the "expect as precondition" style, we would instead describe the -//! reason we _expect_ the `Result` should be `Ok`. With this style we would -//! prefer to write: -//! -//! ```should_panic -//! let path = std::env::var("IMPORTANT_PATH") -//! .expect("env variable `IMPORTANT_PATH` should be set by `wrapper_script.sh`"); -//! ``` -//! -//! The "expect as error message" style does not work as well with the -//! default output of the std panic hooks, and often ends up repeating -//! information that is already communicated by the source error being -//! unwrapped: -//! -//! ```text -//! thread 'main' panicked at 'env variable `IMPORTANT_PATH` is not set: NotPresent', src/main.rs:4:6 -//! ``` -//! -//! In this example we end up mentioning that an env variable is not set, -//! followed by our source message that says the env is not present, the -//! only additional information we're communicating is the name of the -//! environment variable being checked. -//! -//! The "expect as precondition" style instead focuses on source code -//! readability, making it easier to understand what must have gone wrong in -//! situations where panics are being used to represent bugs exclusively. -//! Also, by framing our expect in terms of what "SHOULD" have happened to -//! prevent the source error, we end up introducing new information that is -//! independent from our source error. -//! -//! ```text -//! thread 'main' panicked at 'env variable `IMPORTANT_PATH` should be set by `wrapper_script.sh`: NotPresent', src/main.rs:4:6 -//! ``` -//! -//! In this example we are communicating not only the name of the -//! environment variable that should have been set, but also an explanation -//! for why it should have been set, and we let the source error display as -//! a clear contradiction to our expectation. -//! -//! **Hint**: If you're having trouble remembering how to phrase -//! expect-as-precondition style error messages remember to focus on the word -//! "should" as in "env variable should be set by blah" or "the given binary -//! should be available and executable by the current user". -//! -//! [`panic_any`]: crate::panic::panic_any -//! [`PanicInfo`]: crate::panic::PanicInfo -//! [`catch_unwind`]: crate::panic::catch_unwind -//! [`resume_unwind`]: crate::panic::resume_unwind -//! [`downcast`]: crate::error::Error -//! [`Termination`]: crate::process::Termination -//! [`Try`]: crate::ops::Try -//! [panic hook]: crate::panic::set_hook -//! [`set_hook`]: crate::panic::set_hook -//! [`take_hook`]: crate::panic::take_hook -//! [panic-handler]: <https://doc.rust-lang.org/nomicon/panic-handler.html> -//! [`match`]: ../../std/keyword.match.html -//! [`?`]: ../../std/result/index.html#the-question-mark-operator- - +#![doc = include_str!("../../core/src/error.md")] #![stable(feature = "rust1", since = "1.0.0")] -// A note about crates and the facade: -// -// Originally, the `Error` trait was defined in libcore, and the impls -// were scattered about. However, coherence objected to this -// arrangement, because to create the blanket impls for `Box` required -// knowing that `&str: !Error`, and we have no means to deal with that -// sort of conflict just now. Therefore, for the time being, we have -// moved the `Error` trait into libstd. As we evolve a sol'n to the -// coherence challenge (e.g., specialization, neg impls, etc) we can -// reconsider what crate these items belong in. - #[cfg(test)] mod tests; -use core::array; -use core::convert::Infallible; - -use crate::alloc::{AllocError, LayoutError}; -use crate::any::{Demand, Provider, TypeId}; use crate::backtrace::Backtrace; -use crate::borrow::Cow; -use crate::cell; -use crate::char; -use crate::fmt::{self, Debug, Display, Write}; -use crate::io; -use crate::mem::transmute; -use crate::num; -use crate::str; -use crate::string; -use crate::sync::Arc; -use crate::time; +use crate::fmt::{self, Write}; -/// `Error` is a trait representing the basic expectations for error values, -/// i.e., values of type `E` in [`Result<T, E>`]. -/// -/// Errors must describe themselves through the [`Display`] and [`Debug`] -/// traits. Error messages are typically concise lowercase sentences without -/// trailing punctuation: -/// -/// ``` -/// let err = "NaN".parse::<u32>().unwrap_err(); -/// assert_eq!(err.to_string(), "invalid digit found in string"); -/// ``` -/// -/// Errors may provide cause chain information. [`Error::source()`] is generally -/// used when errors cross "abstraction boundaries". If one module must report -/// an error that is caused by an error from a lower-level module, it can allow -/// accessing that error via [`Error::source()`]. This makes it possible for the -/// high-level module to provide its own errors while also revealing some of the -/// implementation for debugging via `source` chains. #[stable(feature = "rust1", since = "1.0.0")] -#[cfg_attr(not(test), rustc_diagnostic_item = "Error")] -pub trait Error: Debug + Display { - /// The lower-level source of this error, if any. - /// - /// # Examples - /// - /// ``` - /// use std::error::Error; - /// use std::fmt; - /// - /// #[derive(Debug)] - /// struct SuperError { - /// source: 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.source) - /// } - /// } - /// - /// #[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 { source: SuperErrorSideKick }) - /// } - /// - /// fn main() { - /// match get_super_error() { - /// Err(e) => { - /// println!("Error: {e}"); - /// println!("Caused by: {}", e.source().unwrap()); - /// } - /// _ => println!("No error"), - /// } - /// } - /// ``` - #[stable(feature = "error_source", since = "1.30.0")] - fn source(&self) -> Option<&(dyn Error + 'static)> { - None - } - - /// Gets the `TypeId` of `self`. - #[doc(hidden)] - #[unstable( - feature = "error_type_id", - reason = "this is memory-unsafe to override in user code", - issue = "60784" - )] - fn type_id(&self, _: private::Internal) -> TypeId - where - Self: 'static, - { - TypeId::of::<Self>() - } - - /// ``` - /// if let Err(e) = "xc".parse::<u32>() { - /// // Print `e` itself, no need for description(). - /// eprintln!("Error: {e}"); - /// } - /// ``` - #[stable(feature = "rust1", since = "1.0.0")] - #[deprecated(since = "1.42.0", note = "use the Display impl or to_string()")] - fn description(&self) -> &str { - "description() is deprecated; use Display" - } - - #[stable(feature = "rust1", since = "1.0.0")] - #[deprecated( - since = "1.33.0", - note = "replaced by Error::source, which can support downcasting" - )] - #[allow(missing_docs)] - fn cause(&self) -> Option<&dyn Error> { - self.source() - } - - /// Provides type based access to context intended for error reports. - /// - /// Used in conjunction with [`Demand::provide_value`] and [`Demand::provide_ref`] to extract - /// references to member variables from `dyn Error` trait objects. - /// - /// # Example - /// - /// ```rust - /// #![feature(provide_any)] - /// #![feature(error_generic_member_access)] - /// use core::fmt; - /// use core::any::Demand; - /// - /// #[derive(Debug)] - /// struct MyBacktrace { - /// // ... - /// } - /// - /// impl MyBacktrace { - /// fn new() -> MyBacktrace { - /// // ... - /// # MyBacktrace {} - /// } - /// } - /// - /// #[derive(Debug)] - /// struct SourceError { - /// // ... - /// } - /// - /// impl fmt::Display for SourceError { - /// fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { - /// write!(f, "Example Source Error") - /// } - /// } - /// - /// impl std::error::Error for SourceError {} - /// - /// #[derive(Debug)] - /// struct Error { - /// source: SourceError, - /// backtrace: MyBacktrace, - /// } - /// - /// impl fmt::Display for Error { - /// fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { - /// write!(f, "Example Error") - /// } - /// } - /// - /// impl std::error::Error for Error { - /// fn provide<'a>(&'a self, req: &mut Demand<'a>) { - /// req - /// .provide_ref::<MyBacktrace>(&self.backtrace) - /// .provide_ref::<dyn std::error::Error + 'static>(&self.source); - /// } - /// } - /// - /// fn main() { - /// let backtrace = MyBacktrace::new(); - /// let source = SourceError {}; - /// let error = Error { source, backtrace }; - /// let dyn_error = &error as &dyn std::error::Error; - /// let backtrace_ref = dyn_error.request_ref::<MyBacktrace>().unwrap(); - /// - /// assert!(core::ptr::eq(&error.backtrace, backtrace_ref)); - /// } - /// ``` - #[unstable(feature = "error_generic_member_access", issue = "99301")] - #[allow(unused_variables)] - fn provide<'a>(&'a self, req: &mut Demand<'a>) {} -} - -#[unstable(feature = "error_generic_member_access", issue = "99301")] -impl<'b> Provider for dyn Error + 'b { - fn provide<'a>(&'a self, req: &mut Demand<'a>) { - self.provide(req) - } -} +pub use core::error::Error; mod private { // This is a hack to prevent `type_id` from being overridden by `Error` @@ -370,742 +18,10 @@ mod private { pub struct Internal; } -#[stable(feature = "rust1", since = "1.0.0")] -impl<'a, E: Error + 'a> From<E> for Box<dyn Error + 'a> { - /// Converts a type of [`Error`] into a box of dyn [`Error`]. - /// - /// # Examples - /// - /// ``` - /// use std::error::Error; - /// use std::fmt; - /// use std::mem; - /// - /// #[derive(Debug)] - /// struct AnError; - /// - /// impl fmt::Display for AnError { - /// fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { - /// write!(f, "An error") - /// } - /// } - /// - /// impl Error for AnError {} - /// - /// let an_error = AnError; - /// assert!(0 == mem::size_of_val(&an_error)); - /// let a_boxed_error = Box::<dyn Error>::from(an_error); - /// assert!(mem::size_of::<Box<dyn Error>>() == mem::size_of_val(&a_boxed_error)) - /// ``` - fn from(err: E) -> Box<dyn Error + 'a> { - Box::new(err) - } -} - -#[stable(feature = "rust1", since = "1.0.0")] -impl<'a, E: Error + Send + Sync + 'a> From<E> for Box<dyn Error + Send + Sync + 'a> { - /// Converts a type of [`Error`] + [`Send`] + [`Sync`] into a box of - /// dyn [`Error`] + [`Send`] + [`Sync`]. - /// - /// # Examples - /// - /// ``` - /// use std::error::Error; - /// use std::fmt; - /// use std::mem; - /// - /// #[derive(Debug)] - /// struct AnError; - /// - /// impl fmt::Display for AnError { - /// fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { - /// write!(f, "An error") - /// } - /// } - /// - /// impl Error for AnError {} - /// - /// unsafe impl Send for AnError {} - /// - /// unsafe impl Sync for AnError {} - /// - /// let an_error = AnError; - /// assert!(0 == mem::size_of_val(&an_error)); - /// let a_boxed_error = Box::<dyn Error + Send + Sync>::from(an_error); - /// assert!( - /// mem::size_of::<Box<dyn Error + Send + Sync>>() == mem::size_of_val(&a_boxed_error)) - /// ``` - fn from(err: E) -> Box<dyn Error + Send + Sync + 'a> { - Box::new(err) - } -} - -#[stable(feature = "rust1", since = "1.0.0")] -impl From<String> for Box<dyn Error + Send + Sync> { - /// Converts a [`String`] into a box of dyn [`Error`] + [`Send`] + [`Sync`]. - /// - /// # Examples - /// - /// ``` - /// use std::error::Error; - /// use std::mem; - /// - /// let a_string_error = "a string error".to_string(); - /// let a_boxed_error = Box::<dyn Error + Send + Sync>::from(a_string_error); - /// assert!( - /// mem::size_of::<Box<dyn Error + Send + Sync>>() == mem::size_of_val(&a_boxed_error)) - /// ``` - #[inline] - fn from(err: String) -> Box<dyn Error + Send + Sync> { - struct StringError(String); - - impl Error for StringError { - #[allow(deprecated)] - fn description(&self) -> &str { - &self.0 - } - } - - impl Display for StringError { - fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { - Display::fmt(&self.0, f) - } - } - - // Purposefully skip printing "StringError(..)" - impl Debug for StringError { - fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { - Debug::fmt(&self.0, f) - } - } - - Box::new(StringError(err)) - } -} - -#[stable(feature = "string_box_error", since = "1.6.0")] -impl From<String> for Box<dyn Error> { - /// Converts a [`String`] into a box of dyn [`Error`]. - /// - /// # Examples - /// - /// ``` - /// use std::error::Error; - /// use std::mem; - /// - /// let a_string_error = "a string error".to_string(); - /// let a_boxed_error = Box::<dyn Error>::from(a_string_error); - /// assert!(mem::size_of::<Box<dyn Error>>() == mem::size_of_val(&a_boxed_error)) - /// ``` - fn from(str_err: String) -> Box<dyn Error> { - let err1: Box<dyn Error + Send + Sync> = From::from(str_err); - let err2: Box<dyn Error> = err1; - err2 - } -} - -#[stable(feature = "rust1", since = "1.0.0")] -impl<'a> From<&str> for Box<dyn Error + Send + Sync + 'a> { - /// Converts a [`str`] into a box of dyn [`Error`] + [`Send`] + [`Sync`]. - /// - /// [`str`]: prim@str - /// - /// # Examples - /// - /// ``` - /// use std::error::Error; - /// use std::mem; - /// - /// let a_str_error = "a str error"; - /// let a_boxed_error = Box::<dyn Error + Send + Sync>::from(a_str_error); - /// assert!( - /// mem::size_of::<Box<dyn Error + Send + Sync>>() == mem::size_of_val(&a_boxed_error)) - /// ``` - #[inline] - fn from(err: &str) -> Box<dyn Error + Send + Sync + 'a> { - From::from(String::from(err)) - } -} - -#[stable(feature = "string_box_error", since = "1.6.0")] -impl From<&str> for Box<dyn Error> { - /// Converts a [`str`] into a box of dyn [`Error`]. - /// - /// [`str`]: prim@str - /// - /// # Examples - /// - /// ``` - /// use std::error::Error; - /// use std::mem; - /// - /// let a_str_error = "a str error"; - /// let a_boxed_error = Box::<dyn Error>::from(a_str_error); - /// assert!(mem::size_of::<Box<dyn Error>>() == mem::size_of_val(&a_boxed_error)) - /// ``` - fn from(err: &str) -> Box<dyn Error> { - From::from(String::from(err)) - } -} - -#[stable(feature = "cow_box_error", since = "1.22.0")] -impl<'a, 'b> From<Cow<'b, str>> for Box<dyn Error + Send + Sync + 'a> { - /// Converts a [`Cow`] into a box of dyn [`Error`] + [`Send`] + [`Sync`]. - /// - /// # Examples - /// - /// ``` - /// use std::error::Error; - /// use std::mem; - /// use std::borrow::Cow; - /// - /// let a_cow_str_error = Cow::from("a str error"); - /// let a_boxed_error = Box::<dyn Error + Send + Sync>::from(a_cow_str_error); - /// assert!( - /// mem::size_of::<Box<dyn Error + Send + Sync>>() == mem::size_of_val(&a_boxed_error)) - /// ``` - fn from(err: Cow<'b, str>) -> Box<dyn Error + Send + Sync + 'a> { - From::from(String::from(err)) - } -} - -#[stable(feature = "cow_box_error", since = "1.22.0")] -impl<'a> From<Cow<'a, str>> for Box<dyn Error> { - /// Converts a [`Cow`] into a box of dyn [`Error`]. - /// - /// # Examples - /// - /// ``` - /// use std::error::Error; - /// use std::mem; - /// use std::borrow::Cow; - /// - /// let a_cow_str_error = Cow::from("a str error"); - /// let a_boxed_error = Box::<dyn Error>::from(a_cow_str_error); - /// assert!(mem::size_of::<Box<dyn Error>>() == mem::size_of_val(&a_boxed_error)) - /// ``` - fn from(err: Cow<'a, str>) -> Box<dyn Error> { - From::from(String::from(err)) - } -} - -#[unstable(feature = "never_type", issue = "35121")] -impl Error for ! {} - -#[unstable( - feature = "allocator_api", - reason = "the precise API and guarantees it provides may be tweaked.", - issue = "32838" -)] -impl Error for AllocError {} - -#[stable(feature = "alloc_layout", since = "1.28.0")] -impl Error for LayoutError {} - -#[stable(feature = "rust1", since = "1.0.0")] -impl Error for str::ParseBoolError { - #[allow(deprecated)] - fn description(&self) -> &str { - "failed to parse bool" - } -} - -#[stable(feature = "rust1", since = "1.0.0")] -impl Error for str::Utf8Error { - #[allow(deprecated)] - fn description(&self) -> &str { - "invalid utf-8: corrupt contents" - } -} - -#[stable(feature = "rust1", since = "1.0.0")] -impl Error for num::ParseIntError { - #[allow(deprecated)] - fn description(&self) -> &str { - self.__description() - } -} - -#[stable(feature = "try_from", since = "1.34.0")] -impl Error for num::TryFromIntError { - #[allow(deprecated)] - fn description(&self) -> &str { - self.__description() - } -} - -#[stable(feature = "try_from", since = "1.34.0")] -impl Error for array::TryFromSliceError { - #[allow(deprecated)] - fn description(&self) -> &str { - self.__description() - } -} - -#[stable(feature = "rust1", since = "1.0.0")] -impl Error for num::ParseFloatError { - #[allow(deprecated)] - fn description(&self) -> &str { - self.__description() - } -} - -#[stable(feature = "rust1", since = "1.0.0")] -impl Error for string::FromUtf8Error { - #[allow(deprecated)] - fn description(&self) -> &str { - "invalid utf-8" - } -} - -#[stable(feature = "rust1", since = "1.0.0")] -impl Error for string::FromUtf16Error { - #[allow(deprecated)] - fn description(&self) -> &str { - "invalid utf-16" - } -} - -#[stable(feature = "str_parse_error2", since = "1.8.0")] -impl Error for Infallible { - fn description(&self) -> &str { - match *self {} - } -} - -#[stable(feature = "decode_utf16", since = "1.9.0")] -impl Error for char::DecodeUtf16Error { - #[allow(deprecated)] - fn description(&self) -> &str { - "unpaired surrogate found" - } -} - -#[stable(feature = "u8_from_char", since = "1.59.0")] -impl Error for char::TryFromCharError {} - -#[unstable(feature = "map_try_insert", issue = "82766")] -impl<'a, K: Debug + Ord, V: Debug> Error - for crate::collections::btree_map::OccupiedError<'a, K, V> -{ - #[allow(deprecated)] - fn description(&self) -> &str { - "key already exists" - } -} - -#[unstable(feature = "map_try_insert", issue = "82766")] -impl<'a, K: Debug, V: Debug> Error for crate::collections::hash_map::OccupiedError<'a, K, V> { - #[allow(deprecated)] - fn description(&self) -> &str { - "key already exists" - } -} - -#[stable(feature = "box_error", since = "1.8.0")] -impl<T: Error> Error for Box<T> { - #[allow(deprecated, deprecated_in_future)] - fn description(&self) -> &str { - Error::description(&**self) - } - - #[allow(deprecated)] - fn cause(&self) -> Option<&dyn Error> { - Error::cause(&**self) - } - - fn source(&self) -> Option<&(dyn Error + 'static)> { - Error::source(&**self) - } -} - -#[unstable(feature = "thin_box", issue = "92791")] -impl<T: ?Sized + crate::error::Error> crate::error::Error for crate::boxed::ThinBox<T> { - fn source(&self) -> Option<&(dyn crate::error::Error + 'static)> { - use core::ops::Deref; - self.deref().source() - } -} - -#[stable(feature = "error_by_ref", since = "1.51.0")] -impl<'a, T: Error + ?Sized> Error for &'a T { - #[allow(deprecated, deprecated_in_future)] - fn description(&self) -> &str { - Error::description(&**self) - } - - #[allow(deprecated)] - fn cause(&self) -> Option<&dyn Error> { - Error::cause(&**self) - } - - fn source(&self) -> Option<&(dyn Error + 'static)> { - Error::source(&**self) - } - - fn provide<'b>(&'b self, req: &mut Demand<'b>) { - Error::provide(&**self, req); - } -} - -#[stable(feature = "arc_error", since = "1.52.0")] -impl<T: Error + ?Sized> Error for Arc<T> { - #[allow(deprecated, deprecated_in_future)] - fn description(&self) -> &str { - Error::description(&**self) - } - - #[allow(deprecated)] - fn cause(&self) -> Option<&dyn Error> { - Error::cause(&**self) - } - - fn source(&self) -> Option<&(dyn Error + 'static)> { - Error::source(&**self) - } - - fn provide<'a>(&'a self, req: &mut Demand<'a>) { - Error::provide(&**self, req); - } -} - -#[stable(feature = "fmt_error", since = "1.11.0")] -impl Error for fmt::Error { - #[allow(deprecated)] - fn description(&self) -> &str { - "an error occurred when formatting an argument" - } -} - -#[stable(feature = "try_borrow", since = "1.13.0")] -impl Error for cell::BorrowError { - #[allow(deprecated)] - fn description(&self) -> &str { - "already mutably borrowed" - } -} - -#[stable(feature = "try_borrow", since = "1.13.0")] -impl Error for cell::BorrowMutError { - #[allow(deprecated)] - fn description(&self) -> &str { - "already borrowed" - } -} - -#[stable(feature = "try_from", since = "1.34.0")] -impl Error for char::CharTryFromError { - #[allow(deprecated)] - fn description(&self) -> &str { - "converted integer out of range for `char`" - } -} - -#[stable(feature = "char_from_str", since = "1.20.0")] -impl Error for char::ParseCharError { - #[allow(deprecated)] - fn description(&self) -> &str { - self.__description() - } -} - -#[stable(feature = "try_reserve", since = "1.57.0")] -impl Error for alloc::collections::TryReserveError {} - -#[unstable(feature = "duration_checked_float", issue = "83400")] -impl Error for time::FromFloatSecsError {} - -#[stable(feature = "rust1", since = "1.0.0")] -impl Error for alloc::ffi::NulError { - #[allow(deprecated)] - fn description(&self) -> &str { - "nul byte found in data" - } -} - -#[stable(feature = "rust1", since = "1.0.0")] -impl From<alloc::ffi::NulError> for io::Error { - /// Converts a [`alloc::ffi::NulError`] into a [`io::Error`]. - fn from(_: alloc::ffi::NulError) -> io::Error { - io::const_io_error!(io::ErrorKind::InvalidInput, "data provided contains a nul byte") - } -} - -#[stable(feature = "frombyteswithnulerror_impls", since = "1.17.0")] -impl Error for core::ffi::FromBytesWithNulError { - #[allow(deprecated)] - fn description(&self) -> &str { - self.__description() - } -} - -#[unstable(feature = "cstr_from_bytes_until_nul", issue = "95027")] -impl Error for core::ffi::FromBytesUntilNulError {} - -#[stable(feature = "cstring_from_vec_with_nul", since = "1.58.0")] -impl Error for alloc::ffi::FromVecWithNulError {} - -#[stable(feature = "cstring_into", since = "1.7.0")] -impl Error for alloc::ffi::IntoStringError { - #[allow(deprecated)] - fn description(&self) -> &str { - "C string contained non-utf8 bytes" - } - - fn source(&self) -> Option<&(dyn Error + 'static)> { - Some(self.__source()) - } -} - -impl<'a> dyn Error + 'a { - /// Request a reference of type `T` as context about this error. - #[unstable(feature = "error_generic_member_access", issue = "99301")] - pub fn request_ref<T: ?Sized + 'static>(&'a self) -> Option<&'a T> { - core::any::request_ref(self) - } - - /// Request a value of type `T` as context about this error. - #[unstable(feature = "error_generic_member_access", issue = "99301")] - pub fn request_value<T: 'static>(&'a self) -> Option<T> { - core::any::request_value(self) - } -} - -// Copied from `any.rs`. -impl dyn Error + 'static { - /// Returns `true` if the inner type is the same as `T`. - #[stable(feature = "error_downcast", since = "1.3.0")] - #[inline] - pub fn is<T: Error + 'static>(&self) -> bool { - // Get `TypeId` of the type this function is instantiated with. - let t = TypeId::of::<T>(); - - // Get `TypeId` of the type in the trait object (`self`). - let concrete = self.type_id(private::Internal); - - // Compare both `TypeId`s on equality. - t == concrete - } - - /// Returns some reference to the inner value if it is of type `T`, or - /// `None` if it isn't. - #[stable(feature = "error_downcast", since = "1.3.0")] - #[inline] - pub fn downcast_ref<T: Error + 'static>(&self) -> Option<&T> { - if self.is::<T>() { - unsafe { Some(&*(self as *const dyn Error as *const T)) } - } else { - None - } - } - - /// Returns some mutable reference to the inner value if it is of type `T`, or - /// `None` if it isn't. - #[stable(feature = "error_downcast", since = "1.3.0")] - #[inline] - pub fn downcast_mut<T: Error + 'static>(&mut self) -> Option<&mut T> { - if self.is::<T>() { - unsafe { Some(&mut *(self as *mut dyn Error as *mut T)) } - } else { - None - } - } -} - -impl dyn Error + 'static + Send { - /// Forwards to the method defined on the type `dyn Error`. - #[stable(feature = "error_downcast", since = "1.3.0")] - #[inline] - pub fn is<T: Error + 'static>(&self) -> bool { - <dyn Error + 'static>::is::<T>(self) - } - - /// Forwards to the method defined on the type `dyn Error`. - #[stable(feature = "error_downcast", since = "1.3.0")] - #[inline] - pub fn downcast_ref<T: Error + 'static>(&self) -> Option<&T> { - <dyn Error + 'static>::downcast_ref::<T>(self) - } - - /// Forwards to the method defined on the type `dyn Error`. - #[stable(feature = "error_downcast", since = "1.3.0")] - #[inline] - pub fn downcast_mut<T: Error + 'static>(&mut self) -> Option<&mut T> { - <dyn Error + 'static>::downcast_mut::<T>(self) - } - - /// Request a reference of type `T` as context about this error. - #[unstable(feature = "error_generic_member_access", issue = "99301")] - pub fn request_ref<T: ?Sized + 'static>(&self) -> Option<&T> { - <dyn Error>::request_ref(self) - } - - /// Request a value of type `T` as context about this error. - #[unstable(feature = "error_generic_member_access", issue = "99301")] - pub fn request_value<T: 'static>(&self) -> Option<T> { - <dyn Error>::request_value(self) - } -} - -impl dyn Error + 'static + Send + Sync { - /// Forwards to the method defined on the type `dyn Error`. - #[stable(feature = "error_downcast", since = "1.3.0")] - #[inline] - pub fn is<T: Error + 'static>(&self) -> bool { - <dyn Error + 'static>::is::<T>(self) - } - - /// Forwards to the method defined on the type `dyn Error`. - #[stable(feature = "error_downcast", since = "1.3.0")] - #[inline] - pub fn downcast_ref<T: Error + 'static>(&self) -> Option<&T> { - <dyn Error + 'static>::downcast_ref::<T>(self) - } - - /// Forwards to the method defined on the type `dyn Error`. - #[stable(feature = "error_downcast", since = "1.3.0")] - #[inline] - pub fn downcast_mut<T: Error + 'static>(&mut self) -> Option<&mut T> { - <dyn Error + 'static>::downcast_mut::<T>(self) - } - - /// Request a reference of type `T` as context about this error. - #[unstable(feature = "error_generic_member_access", issue = "99301")] - pub fn request_ref<T: ?Sized + 'static>(&self) -> Option<&T> { - <dyn Error>::request_ref(self) - } - - /// Request a value of type `T` as context about this error. - #[unstable(feature = "error_generic_member_access", issue = "99301")] - pub fn request_value<T: 'static>(&self) -> Option<T> { - <dyn Error>::request_value(self) - } -} - -impl dyn Error { - #[inline] - #[stable(feature = "error_downcast", since = "1.3.0")] - /// Attempts to downcast the box to a concrete type. - pub fn downcast<T: Error + 'static>(self: Box<Self>) -> Result<Box<T>, Box<dyn Error>> { - if self.is::<T>() { - unsafe { - let raw: *mut dyn Error = Box::into_raw(self); - Ok(Box::from_raw(raw as *mut T)) - } - } else { - Err(self) - } - } - - /// Returns an iterator starting with the current error and continuing with - /// recursively calling [`Error::source`]. - /// - /// If you want to omit the current error and only use its sources, - /// use `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))); - /// - /// // let err : Box<Error> = b.into(); // or - /// 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()); - /// ``` - #[unstable(feature = "error_iter", issue = "58520")] - #[inline] - pub fn chain(&self) -> Chain<'_> { - Chain { current: Some(self) } - } -} - -/// An iterator over an [`Error`] and its sources. -/// -/// If you want to omit the initial error and only process -/// its sources, use `skip(1)`. -#[unstable(feature = "error_iter", issue = "58520")] -#[derive(Clone, Debug)] -pub struct Chain<'a> { - current: Option<&'a (dyn Error + 'static)>, -} - -#[unstable(feature = "error_iter", issue = "58520")] -impl<'a> Iterator for Chain<'a> { - type Item = &'a (dyn Error + 'static); - - fn next(&mut self) -> Option<Self::Item> { - let current = self.current; - self.current = self.current.and_then(Error::source); - current - } -} - -impl dyn Error + Send { - #[inline] - #[stable(feature = "error_downcast", since = "1.3.0")] - /// Attempts to downcast the box to a concrete type. - pub fn downcast<T: Error + 'static>(self: Box<Self>) -> Result<Box<T>, Box<dyn Error + Send>> { - let err: Box<dyn Error> = self; - <dyn Error>::downcast(err).map_err(|s| unsafe { - // Reapply the `Send` marker. - transmute::<Box<dyn Error>, Box<dyn Error + Send>>(s) - }) - } -} - -impl dyn Error + Send + Sync { - #[inline] - #[stable(feature = "error_downcast", since = "1.3.0")] - /// Attempts to downcast the box to a concrete type. - pub fn downcast<T: Error + 'static>(self: Box<Self>) -> Result<Box<T>, Box<Self>> { - let err: Box<dyn Error> = self; - <dyn Error>::downcast(err).map_err(|s| unsafe { - // Reapply the `Send + Sync` marker. - transmute::<Box<dyn Error>, Box<dyn Error + Send + Sync>>(s) - }) - } -} - /// An error reporter that prints an error and its sources. /// -/// Report also exposes configuration options for formatting the error chain, either entirely on a -/// single line, or in multi-line format with each cause in the error chain on a new line. +/// Report also exposes configuration options for formatting the error sources, either entirely on a +/// single line, or in multi-line format with each source on a new line. /// /// `Report` only requires that the wrapped error implement `Error`. It doesn't require that the /// wrapped error be `Send`, `Sync`, or `'static`. @@ -1246,7 +162,7 @@ impl dyn Error + Send + Sync { /// # Err(SuperError { source: SuperErrorSideKick }) /// # } /// -/// fn main() -> Result<(), Report> { +/// fn main() -> Result<(), Report<SuperError>> { /// get_super_error()?; /// Ok(()) /// } @@ -1293,7 +209,7 @@ impl dyn Error + Send + Sync { /// # Err(SuperError { source: SuperErrorSideKick }) /// # } /// -/// fn main() -> Result<(), Report> { +/// fn main() -> Result<(), Report<SuperError>> { /// get_super_error() /// .map_err(Report::from) /// .map_err(|r| r.pretty(true).show_backtrace(true))?; @@ -1450,11 +366,10 @@ impl<E> Report<E> { /// /// **Note**: Report will search for the first `Backtrace` it can find starting from the /// outermost error. In this example it will display the backtrace from the second error in the - /// chain, `SuperErrorSideKick`. + /// sources, `SuperErrorSideKick`. /// /// ```rust /// #![feature(error_reporter)] - /// #![feature(backtrace)] /// #![feature(provide_any)] /// #![feature(error_generic_member_access)] /// # use std::error::Error; @@ -1489,9 +404,8 @@ impl<E> Report<E> { /// } /// /// impl Error for SuperErrorSideKick { - /// fn provide<'a>(&'a self, req: &mut Demand<'a>) { - /// req - /// .provide_ref::<Backtrace>(&self.backtrace); + /// fn provide<'a>(&'a self, demand: &mut Demand<'a>) { + /// demand.provide_ref::<Backtrace>(&self.backtrace); /// } /// } /// @@ -1548,73 +462,7 @@ where let backtrace = backtrace.or_else(|| { self.error .source() - .map(|source| source.chain().find_map(|source| source.request_ref())) - .flatten() - }); - backtrace - } - - /// Format the report as a single line. - #[unstable(feature = "error_reporter", issue = "90172")] - fn fmt_singleline(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { - write!(f, "{}", self.error)?; - - let sources = self.error.source().into_iter().flat_map(<dyn Error>::chain); - - for cause in sources { - write!(f, ": {cause}")?; - } - - Ok(()) - } - - /// Format the report as multiple lines, with each error cause on its own line. - #[unstable(feature = "error_reporter", issue = "90172")] - fn fmt_multiline(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { - let error = &self.error; - - write!(f, "{error}")?; - - if let Some(cause) = error.source() { - write!(f, "\n\nCaused by:")?; - - let multiple = cause.source().is_some(); - - for (ind, error) in cause.chain().enumerate() { - writeln!(f)?; - let mut indented = Indented { inner: f }; - if multiple { - write!(indented, "{ind: >4}: {error}")?; - } else { - write!(indented, " {error}")?; - } - } - } - - if self.show_backtrace { - let backtrace = self.backtrace(); - - if let Some(backtrace) = backtrace { - let backtrace = backtrace.to_string(); - - f.write_str("\n\nStack backtrace:\n")?; - f.write_str(backtrace.trim_end())?; - } - } - - Ok(()) - } -} - -impl Report<Box<dyn Error>> { - fn backtrace(&self) -> Option<&Backtrace> { - // have to grab the backtrace on the first error directly since that error may not be - // 'static - let backtrace = self.error.request_ref(); - let backtrace = backtrace.or_else(|| { - self.error - .source() - .map(|source| source.chain().find_map(|source| source.request_ref())) + .map(|source| source.sources().find_map(|source| source.request_ref())) .flatten() }); backtrace @@ -1625,7 +473,7 @@ impl Report<Box<dyn Error>> { fn fmt_singleline(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { write!(f, "{}", self.error)?; - let sources = self.error.source().into_iter().flat_map(<dyn Error>::chain); + let sources = self.error.source().into_iter().flat_map(<dyn Error>::sources); for cause in sources { write!(f, ": {cause}")?; @@ -1646,7 +494,7 @@ impl Report<Box<dyn Error>> { let multiple = cause.source().is_some(); - for (ind, error) in cause.chain().enumerate() { + for (ind, error) in cause.sources().enumerate() { writeln!(f)?; let mut indented = Indented { inner: f }; if multiple { @@ -1683,17 +531,6 @@ where } #[unstable(feature = "error_reporter", issue = "90172")] -impl<'a, E> From<E> for Report<Box<dyn Error + 'a>> -where - E: Error + 'a, -{ - fn from(error: E) -> Self { - let error = box error; - Report { error, show_backtrace: false, pretty: false } - } -} - -#[unstable(feature = "error_reporter", issue = "90172")] impl<E> fmt::Display for Report<E> where E: Error, @@ -1703,13 +540,6 @@ where } } -#[unstable(feature = "error_reporter", issue = "90172")] -impl fmt::Display for Report<Box<dyn Error>> { - fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { - if self.pretty { self.fmt_multiline(f) } else { self.fmt_singleline(f) } - } -} - // This type intentionally outputs the same format for `Display` and `Debug`for // situations where you unwrap a `Report` or return it from main. #[unstable(feature = "error_reporter", issue = "90172")] |