/// assert_eq!(err.to_string(), "invalid digit found in string");
/// ```
///
-/// Errors may provide cause chain information. [`Error::source()`] is generally
+/// Errors may provide cause 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.
+/// implementation for debugging.
#[stable(feature = "rust1", since = "1.0.0")]
#[cfg_attr(not(test), rustc_diagnostic_item = "Error")]
#[cfg(bootstrap)]
/// }
///
/// impl std::error::Error for Error {
- /// fn provide<'a>(&'a self, req: &mut Demand<'a>) {
- /// req
+ /// fn provide<'a>(&'a self, demand: &mut Demand<'a>) {
+ /// demand
/// .provide_ref::<MyBacktrace>(&self.backtrace)
/// .provide_ref::<dyn std::error::Error + 'static>(&self.source);
/// }
/// ```
#[unstable(feature = "error_generic_member_access", issue = "99301")]
#[allow(unused_variables)]
- fn provide<'a>(&'a self, req: &mut Demand<'a>) {}
+ fn provide<'a>(&'a self, demand: &mut Demand<'a>) {}
}
#[cfg(bootstrap)]
#[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)
+ fn provide<'a>(&'a self, demand: &mut Demand<'a>) {
+ self.provide(demand)
}
}
Error::source(&**self)
}
- fn provide<'b>(&'b self, req: &mut Demand<'b>) {
- Error::provide(&**self, req);
+ fn provide<'b>(&'b self, demand: &mut Demand<'b>) {
+ Error::provide(&**self, demand);
}
}
Error::source(&**self)
}
- fn provide<'a>(&'a self, req: &mut Demand<'a>) {
- Error::provide(&**self, req);
+ fn provide<'a>(&'a self, demand: &mut Demand<'a>) {
+ Error::provide(&**self, demand);
}
}
/// // let err : Box<Error> = b.into(); // or
/// let err = &b as &(dyn Error);
///
- /// let mut iter = err.chain();
+ /// let mut iter = err.sources();
///
/// assert_eq!("B".to_string(), iter.next().unwrap().to_string());
/// assert_eq!("A".to_string(), iter.next().unwrap().to_string());
/// ```
#[unstable(feature = "error_iter", issue = "58520")]
#[inline]
- pub fn chain(&self) -> Chain<'_> {
- Chain { current: Some(self) }
+ pub fn sources(&self) -> Sources<'_> {
+ // You may think this method would be better in the Error trait, and you'd be right.
+ // Unfortunately that doesn't work, not because of the object safety rules but because we
+ // save a reference to self in Sources below as a trait object. If this method was
+ // declared in Error, then self would have the type &T where T is some concrete type which
+ // implements Error. We would need to coerce self to have type &dyn Error, but that requires
+ // that Self has a known size (i.e., Self: Sized). We can't put that bound on Error
+ // since that would forbid Error trait objects, and we can't put that bound on the method
+ // because that means the method can't be called on trait objects (we'd also need the
+ // 'static bound, but that isn't allowed because methods with bounds on Self other than
+ // Sized are not object-safe). Requiring an Unsize bound is not backwards compatible.
+ //
+ // Two possible solutions are to start the iterator at self.source() instead of self (see
+ // discussion on the tracking issue), or to wait for dyn* to exist (which would then permit
+ // the coercion).
+
+ Sources { current: Some(self) }
}
}
#[unstable(feature = "error_iter", issue = "58520")]
#[derive(Clone, Debug)]
#[cfg(bootstrap)]
-pub struct Chain<'a> {
+pub struct Sources<'a> {
current: Option<&'a (dyn Error + 'static)>,
}
#[cfg(bootstrap)]
#[unstable(feature = "error_iter", issue = "58520")]
-impl<'a> Iterator for Chain<'a> {
+impl<'a> Iterator for Sources<'a> {
type Item = &'a (dyn Error + 'static);
fn next(&mut self) -> Option<Self::Item> {
/// 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`.
///
/// **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)]
/// }
///
/// 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);
/// }
/// }
///
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
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}")?;
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 {
projects / rust.git / blobdiff