/// [`source`]: trait.Error.html#method.source
#[stable(feature = "rust1", since = "1.0.0")]
pub trait Error: Debug + Display {
- /// **This method is soft-deprecated.**
- ///
- /// Although using it won’t cause compilation warning,
- /// new code should use [`Display`] instead
- /// and new `impl`s can omit it.
- ///
- /// To obtain error description as a string, use `to_string()`.
- ///
- /// [`Display`]: ../fmt/trait.Display.html
- ///
- /// # Examples
- ///
- /// ```
- /// match "xc".parse::<u32>() {
- /// Err(e) => {
- /// // Print `e` itself, not `e.description()`.
- /// println!("Error: {}", e);
- /// }
- /// _ => println!("No error"),
- /// }
- /// ```
- #[stable(feature = "rust1", since = "1.0.0")]
- fn description(&self) -> &str {
- "description() is deprecated; use Display"
- }
-
- /// The lower-level cause of this error, if any.
- ///
- /// # 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 cause(&self) -> Option<&dyn Error> {
- /// 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.description());
- /// println!("Caused by: {}", e.cause().unwrap());
- /// }
- /// _ => println!("No error"),
- /// }
- /// }
- /// ```
- #[stable(feature = "rust1", since = "1.0.0")]
- #[rustc_deprecated(
- since = "1.33.0",
- reason = "replaced by Error::source, which can support \
- downcasting"
- )]
- fn cause(&self) -> Option<&dyn Error> {
- self.source()
- }
-
/// The lower-level source of this error, if any.
///
/// # Examples
fn backtrace(&self) -> Option<&Backtrace> {
None
}
+
+ /// ```
+ /// if let Err(e) = "xc".parse::<u32>() {
+ /// // Print `e` itself, no need for description().
+ /// eprintln!("Error: {}", e);
+ /// }
+ /// ```
+ #[stable(feature = "rust1", since = "1.0.0")]
+ #[rustc_deprecated(since = "1.41.0", reason = "use the Display impl or to_string()")]
+ fn description(&self) -> &str {
+ "description() is deprecated; use Display"
+ }
+
+ #[stable(feature = "rust1", since = "1.0.0")]
+ #[rustc_deprecated(
+ since = "1.33.0",
+ reason = "replaced by Error::source, which can support downcasting"
+ )]
+ #[allow(missing_docs)]
+ fn cause(&self) -> Option<&dyn Error> {
+ self.source()
+ }
}
mod private {
/// 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
}
/// 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))
}
}
#[unstable(feature = "never_type", issue = "35121")]
-impl Error for ! {
- fn description(&self) -> &str {
- *self
- }
-}
+impl Error for ! {}
#[unstable(
feature = "allocator_api",
reason = "the precise API and guarantees it provides may be tweaked.",
issue = "32838"
)]
-impl Error for AllocErr {
- fn description(&self) -> &str {
- "memory allocation failed"
- }
-}
+impl Error for AllocErr {}
#[unstable(
feature = "allocator_api",
reason = "the precise API and guarantees it provides may be tweaked.",
issue = "32838"
)]
-impl Error for LayoutErr {
- fn description(&self) -> &str {
- "invalid parameters to Layout::from_size_align"
- }
-}
+impl Error for LayoutErr {}
#[unstable(
feature = "allocator_api",
reason = "the precise API and guarantees it provides may be tweaked.",
issue = "32838"
)]
-impl Error for CannotReallocInPlace {
- fn description(&self) -> &str {
- CannotReallocInPlace::description(self)
- }
-}
+impl Error for CannotReallocInPlace {}
#[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 = "decode_utf16", since = "1.9.0")]
impl Error for char::DecodeUtf16Error {
+ #[allow(deprecated)]
fn description(&self) -> &str {
"unpaired surrogate found"
}
#[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)
}
#[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()
}
}
}
- impl Error for A {
- fn description(&self) -> &str {
- "A-desc"
- }
- }
- impl Error for B {
- fn description(&self) -> &str {
- "A-desc"
- }
- }
+ impl Error for A {}
+ impl Error for B {}
#[test]
fn downcasting() {
projects / rust.git / blobdiff