pub struct Error { /* private fields */ }
Expand description
Implementations§
source§impl Error
impl Error
sourcepub fn new<E>(kind: ErrorKind, error: E) -> Error
pub fn new<E>(kind: ErrorKind, error: E) -> Error
Creates a new I/O error from a known kind of error as well as an arbitrary error payload.
This function is used to generically create I/O errors which do not
originate from the OS itself. The error
argument is an arbitrary
payload which will be contained in this Error
.
Note that this function allocates memory on the heap.
If no extra payload is required, use the From
conversion from
ErrorKind
.
§Examples
use std::io::{Error, ErrorKind};
// errors can be created from strings
let custom_error = Error::new(ErrorKind::Other, "oh no!");
// errors can also be created from other errors
let custom_error2 = Error::new(ErrorKind::Interrupted, custom_error);
// creating an error without payload (and without memory allocation)
let eof_error = Error::from(ErrorKind::UnexpectedEof);
Run1.74.0 · sourcepub fn other<E>(error: E) -> Error
pub fn other<E>(error: E) -> Error
Creates a new I/O error from an arbitrary error payload.
This function is used to generically create I/O errors which do not
originate from the OS itself. It is a shortcut for Error::new
with ErrorKind::Other
.
§Examples
use std::io::Error;
// errors can be created from strings
let custom_error = Error::other("oh no!");
// errors can also be created from other errors
let custom_error2 = Error::other(custom_error);
Runsourcepub fn last_os_error() -> Error
pub fn last_os_error() -> Error
Returns an error representing the last OS error which occurred.
This function reads the value of errno
for the target platform (e.g.
GetLastError
on Windows) and will return a corresponding instance of
Error
for the error code.
This should be called immediately after a call to a platform function, otherwise the state of the error value is indeterminate. In particular, other standard library functions may call platform functions that may (or may not) reset the error value even if they succeed.
§Examples
use std::io::Error;
let os_error = Error::last_os_error();
println!("last OS error: {os_error:?}");
Runsourcepub fn from_raw_os_error(code: RawOsError) -> Error
pub fn from_raw_os_error(code: RawOsError) -> Error
Creates a new instance of an Error
from a particular OS error code.
§Examples
On Linux:
use std::io;
let error = io::Error::from_raw_os_error(22);
assert_eq!(error.kind(), io::ErrorKind::InvalidInput);
RunOn Windows:
use std::io;
let error = io::Error::from_raw_os_error(10022);
assert_eq!(error.kind(), io::ErrorKind::InvalidInput);
Runsourcepub fn raw_os_error(&self) -> Option<RawOsError>
pub fn raw_os_error(&self) -> Option<RawOsError>
Returns the OS error that this error represents (if any).
If this Error
was constructed via last_os_error
or
from_raw_os_error
, then this function will return Some
, otherwise
it will return None
.
§Examples
use std::io::{Error, ErrorKind};
fn print_os_error(err: &Error) {
if let Some(raw_os_err) = err.raw_os_error() {
println!("raw OS error: {raw_os_err:?}");
} else {
println!("Not an OS error");
}
}
fn main() {
// Will print "raw OS error: ...".
print_os_error(&Error::last_os_error());
// Will print "Not an OS error".
print_os_error(&Error::new(ErrorKind::Other, "oh no!"));
}
Run1.3.0 · sourcepub fn get_ref(&self) -> Option<&(dyn Error + Send + Sync + 'static)>
pub fn get_ref(&self) -> Option<&(dyn Error + Send + Sync + 'static)>
Returns a reference to the inner error wrapped by this error (if any).
If this Error
was constructed via new
then this function will
return Some
, otherwise it will return None
.
§Examples
use std::io::{Error, ErrorKind};
fn print_error(err: &Error) {
if let Some(inner_err) = err.get_ref() {
println!("Inner error: {inner_err:?}");
} else {
println!("No inner error");
}
}
fn main() {
// Will print "No inner error".
print_error(&Error::last_os_error());
// Will print "Inner error: ...".
print_error(&Error::new(ErrorKind::Other, "oh no!"));
}
Run1.3.0 · sourcepub fn get_mut(&mut self) -> Option<&mut (dyn Error + Send + Sync + 'static)>
pub fn get_mut(&mut self) -> Option<&mut (dyn Error + Send + Sync + 'static)>
Returns a mutable reference to the inner error wrapped by this error (if any).
If this Error
was constructed via new
then this function will
return Some
, otherwise it will return None
.
§Examples
use std::io::{Error, ErrorKind};
use std::{error, fmt};
use std::fmt::Display;
#[derive(Debug)]
struct MyError {
v: String,
}
impl MyError {
fn new() -> MyError {
MyError {
v: "oh no!".to_string()
}
}
fn change_message(&mut self, new_message: &str) {
self.v = new_message.to_string();
}
}
impl error::Error for MyError {}
impl Display for MyError {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
write!(f, "MyError: {}", &self.v)
}
}
fn change_error(mut err: Error) -> Error {
if let Some(inner_err) = err.get_mut() {
inner_err.downcast_mut::<MyError>().unwrap().change_message("I've been changed!");
}
err
}
fn print_error(err: &Error) {
if let Some(inner_err) = err.get_ref() {
println!("Inner error: {inner_err}");
} else {
println!("No inner error");
}
}
fn main() {
// Will print "No inner error".
print_error(&change_error(Error::last_os_error()));
// Will print "Inner error: ...".
print_error(&change_error(Error::new(ErrorKind::Other, MyError::new())));
}
Run1.3.0 · sourcepub fn into_inner(self) -> Option<Box<dyn Error + Send + Sync>>
pub fn into_inner(self) -> Option<Box<dyn Error + Send + Sync>>
Consumes the Error
, returning its inner error (if any).
If this Error
was constructed via new
then this function will
return Some
, otherwise it will return None
.
§Examples
use std::io::{Error, ErrorKind};
fn print_error(err: Error) {
if let Some(inner_err) = err.into_inner() {
println!("Inner error: {inner_err}");
} else {
println!("No inner error");
}
}
fn main() {
// Will print "No inner error".
print_error(Error::last_os_error());
// Will print "Inner error: ...".
print_error(Error::new(ErrorKind::Other, "oh no!"));
}
Runsourcepub fn downcast<E>(self) -> Result<E, Self>
🔬This is a nightly-only experimental API. (io_error_downcast
#99262)
pub fn downcast<E>(self) -> Result<E, Self>
io_error_downcast
#99262)Attempt to downcast the inner error to E
if any.
If this Error
was constructed via new
then this function will
attempt to perform downgrade on it, otherwise it will return Err
.
If the downcast succeeds, it will return Ok
, otherwise it will also
return Err
.
§Examples
#![feature(io_error_downcast)]
use std::fmt;
use std::io;
use std::error::Error;
#[derive(Debug)]
enum E {
Io(io::Error),
SomeOtherVariant,
}
impl fmt::Display for E {
// ...
}
impl Error for E {}
impl From<io::Error> for E {
fn from(err: io::Error) -> E {
err.downcast::<E>()
.unwrap_or_else(E::Io)
}
}
impl From<E> for io::Error {
fn from(err: E) -> io::Error {
match err {
E::Io(io_error) => io_error,
e => io::Error::new(io::ErrorKind::Other, e),
}
}
}
let e = E::SomeOtherVariant;
// Convert it to an io::Error
let io_error = io::Error::from(e);
// Cast it back to the original variant
let e = E::from(io_error);
assert!(matches!(e, E::SomeOtherVariant));
let io_error = io::Error::from(io::ErrorKind::AlreadyExists);
// Convert it to E
let e = E::from(io_error);
// Cast it back to the original variant
let io_error = io::Error::from(e);
assert_eq!(io_error.kind(), io::ErrorKind::AlreadyExists);
assert!(io_error.get_ref().is_none());
assert!(io_error.raw_os_error().is_none());
Runsourcepub fn kind(&self) -> ErrorKind
pub fn kind(&self) -> ErrorKind
Returns the corresponding ErrorKind
for this error.
This may be a value set by Rust code constructing custom io::Error
s,
or if this io::Error
was sourced from the operating system,
it will be a value inferred from the system’s error encoding.
See last_os_error
for more details.
§Examples
use std::io::{Error, ErrorKind};
fn print_error(err: Error) {
println!("{:?}", err.kind());
}
fn main() {
// As no error has (visibly) occurred, this may print anything!
// It likely prints a placeholder for unidentified (non-)errors.
print_error(Error::last_os_error());
// Will print "AddrInUse".
print_error(Error::new(ErrorKind::AddrInUse, "oh no!"));
}
RunTrait Implementations§
source§impl Error for Error
impl Error for Error
source§fn description(&self) -> &str
fn description(&self) -> &str
source§fn cause(&self) -> Option<&dyn Error>
fn cause(&self) -> Option<&dyn Error>
1.14.0 · source§impl From<ErrorKind> for Error
impl From<ErrorKind> for Error
Intended for use for errors not exposed to the user, where allocating onto the heap (for normal construction via Error::new) is too costly.