cd6d9eab5d
* `core` - for the core crate * `hash` - hashing * `io` - io * `path` - path * `alloc` - alloc crate * `rand` - rand crate * `collections` - collections crate * `std_misc` - other parts of std * `test` - test crate * `rustc_private` - everything else
140 lines
4.4 KiB
Rust
140 lines
4.4 KiB
Rust
// Copyright 2014 The Rust Project Developers. See the COPYRIGHT
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// file at the top-level directory of this distribution and at
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// http://rust-lang.org/COPYRIGHT.
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//
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// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
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// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
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// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
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// option. This file may not be copied, modified, or distributed
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// except according to those terms.
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//! Traits for working with Errors.
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//!
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//! # The `Error` trait
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//!
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//! `Error` is a trait representing the basic expectations for error values,
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//! i.e. values of type `E` in `Result<T, E>`. At a minimum, errors must provide
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//! a description, but they may optionally provide additional detail and cause
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//! chain information:
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//!
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//! ```
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//! trait Error {
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//! fn description(&self) -> &str;
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//!
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//! fn detail(&self) -> Option<String> { None }
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//! fn cause(&self) -> Option<&Error> { None }
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//! }
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//! ```
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//!
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//! The `cause` method is generally used when errors cross "abstraction
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//! boundaries", i.e. when a one module must report an error that is "caused"
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//! by an error from a lower-level module. This setup makes it possible for the
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//! high-level module to provide its own errors that do not commit to any
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//! particular implementation, but also reveal some of its implementation for
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//! debugging via `cause` chains.
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//!
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//! # The `FromError` trait
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//!
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//! `FromError` is a simple trait that expresses conversions between different
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//! error types. To provide maximum flexibility, it does not require either of
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//! the types to actually implement the `Error` trait, although this will be the
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//! common case.
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//!
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//! The main use of this trait is in the `try!` macro, which uses it to
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//! automatically convert a given error to the error specified in a function's
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//! return type.
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//!
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//! For example,
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//!
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//! ```
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//! use std::error::FromError;
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//! use std::io::{File, IoError};
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//! use std::os::{MemoryMap, MapError};
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//! use std::path::Path;
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//!
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//! enum MyError {
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//! Io(IoError),
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//! Map(MapError)
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//! }
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//!
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//! impl FromError<IoError> for MyError {
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//! fn from_error(err: IoError) -> MyError {
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//! MyError::Io(err)
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//! }
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//! }
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//!
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//! impl FromError<MapError> for MyError {
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//! fn from_error(err: MapError) -> MyError {
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//! MyError::Map(err)
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//! }
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//! }
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//!
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//! #[allow(unused_variables)]
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//! fn open_and_map() -> Result<(), MyError> {
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//! let f = try!(File::open(&Path::new("foo.txt")));
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//! let m = try!(MemoryMap::new(0, &[]));
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//! // do something interesting here...
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//! Ok(())
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//! }
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//! ```
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#![stable(feature = "grandfathered", since = "1.0.0")]
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use prelude::v1::*;
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use str::Utf8Error;
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use string::{FromUtf8Error, FromUtf16Error};
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/// Base functionality for all errors in Rust.
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#[unstable(feature = "std_misc",
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reason = "the exact API of this trait may change")]
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pub trait Error {
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/// A short description of the error; usually a static string.
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fn description(&self) -> &str;
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/// A detailed description of the error, usually including dynamic information.
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fn detail(&self) -> Option<String> { None }
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/// The lower-level cause of this error, if any.
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fn cause(&self) -> Option<&Error> { None }
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}
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/// A trait for types that can be converted from a given error type `E`.
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#[stable(feature = "grandfathered", since = "1.0.0")]
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pub trait FromError<E> {
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/// Perform the conversion.
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#[stable(feature = "grandfathered", since = "1.0.0")]
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fn from_error(err: E) -> Self;
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}
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// Any type is convertable from itself
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#[stable(feature = "grandfathered", since = "1.0.0")]
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impl<E> FromError<E> for E {
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fn from_error(err: E) -> E {
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err
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}
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}
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#[stable(feature = "grandfathered", since = "1.0.0")]
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impl Error for Utf8Error {
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fn description(&self) -> &str {
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match *self {
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Utf8Error::TooShort => "invalid utf-8: not enough bytes",
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Utf8Error::InvalidByte(..) => "invalid utf-8: corrupt contents",
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}
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}
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fn detail(&self) -> Option<String> { Some(self.to_string()) }
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}
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#[stable(feature = "grandfathered", since = "1.0.0")]
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impl Error for FromUtf8Error {
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fn description(&self) -> &str { "invalid utf-8" }
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fn detail(&self) -> Option<String> { Some(self.to_string()) }
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}
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#[stable(feature = "grandfathered", since = "1.0.0")]
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impl Error for FromUtf16Error {
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fn description(&self) -> &str { "invalid utf-16" }
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}
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