Auto merge of #25816 - sfackler:io-error-delegation, r=alexcrichton
The first commit simply forwards `io::Error`'s `cause` implementation to the inner error. The second commit adds accessor methods for the inner error. Method names mirror those used elsewhere like `BufReader`. r? @alexcrichton
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commit
99c2f779d2
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@ -129,9 +129,7 @@ impl Error {
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///
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/// This function is used to generically create I/O errors which do not
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/// originate from the OS itself. The `error` argument is an arbitrary
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/// payload which will be contained in this `Error`. Accessors as well as
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/// downcasting will soon be added to this type as well to access the custom
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/// information.
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/// payload which will be contained in this `Error`.
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///
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/// # Examples
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///
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@ -174,8 +172,9 @@ impl Error {
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/// Returns the OS error that this error represents (if any).
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///
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/// If this `Error` was constructed via `last_os_error` then this function
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/// will return `Some`, otherwise it will return `None`.
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/// If this `Error` was constructed via `last_os_error` or
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/// `from_raw_os_error`, then this function will return `Some`, otherwise
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/// it will return `None`.
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#[stable(feature = "rust1", since = "1.0.0")]
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pub fn raw_os_error(&self) -> Option<i32> {
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match self.repr {
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@ -184,6 +183,46 @@ impl Error {
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}
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}
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/// Returns a reference to the inner error wrapped by this error (if any).
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///
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/// If this `Error` was constructed via `new` then this function will
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/// return `Some`, otherwise it will return `None`.
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#[unstable(feature = "io_error_inner",
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reason = "recently added and requires UFCS to downcast")]
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pub fn get_ref(&self) -> Option<&(error::Error+Send+Sync+'static)> {
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match self.repr {
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Repr::Os(..) => None,
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Repr::Custom(ref c) => Some(&*c.error),
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}
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}
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/// Returns a mutable reference to the inner error wrapped by this error
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/// (if any).
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///
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/// If this `Error` was constructed via `new` then this function will
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/// return `Some`, otherwise it will return `None`.
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#[unstable(feature = "io_error_inner",
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reason = "recently added and requires UFCS to downcast")]
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pub fn get_mut(&mut self) -> Option<&mut (error::Error+Send+Sync+'static)> {
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match self.repr {
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Repr::Os(..) => None,
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Repr::Custom(ref mut c) => Some(&mut *c.error),
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}
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}
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/// Consumes the `Error`, returning its inner error (if any).
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///
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/// If this `Error` was constructed via `new` then this function will
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/// return `Some`, otherwise it will return `None`.
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#[unstable(feature = "io_error_inner",
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reason = "recently added and requires UFCS to downcast")]
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pub fn into_inner(self) -> Option<Box<error::Error+Send+Sync>> {
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match self.repr {
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Repr::Os(..) => None,
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Repr::Custom(c) => Some(c.error)
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}
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}
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/// Returns the corresponding `ErrorKind` for this error.
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#[stable(feature = "rust1", since = "1.0.0")]
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pub fn kind(&self) -> ErrorKind {
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@ -215,9 +254,52 @@ impl error::Error for Error {
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Repr::Custom(ref c) => c.error.description(),
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}
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}
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fn cause(&self) -> Option<&error::Error> {
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match self.repr {
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Repr::Os(..) => None,
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Repr::Custom(ref c) => c.error.cause(),
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}
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}
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}
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fn _assert_error_is_sync_send() {
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fn _is_sync_send<T: Sync+Send>() {}
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_is_sync_send::<Error>();
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}
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#[cfg(test)]
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mod test {
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use prelude::v1::*;
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use super::{Error, ErrorKind};
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use error;
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use error::Error as error_Error;
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use fmt;
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#[test]
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fn test_downcasting() {
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#[derive(Debug)]
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struct TestError;
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impl fmt::Display for TestError {
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fn fmt(&self, fmt: &mut fmt::Formatter) -> fmt::Result {
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Ok(())
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}
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}
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impl error::Error for TestError {
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fn description(&self) -> &str {
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"asdf"
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}
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}
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// we have to call all of these UFCS style right now since method
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// resolution won't implicitly drop the Send+Sync bounds
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let mut err = Error::new(ErrorKind::Other, TestError);
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assert!(error::Error::is::<TestError>(err.get_ref().unwrap()));
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assert_eq!("asdf", err.get_ref().unwrap().description());
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assert!(error::Error::is::<TestError>(err.get_mut().unwrap()));
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let extracted = err.into_inner().unwrap();
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error::Error::downcast::<TestError>(extracted).unwrap();
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}
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}
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