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Add error module from libstd

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Fenrir 8 years ago
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  1. 456
      src/error.rs
  2. 4
      src/lib.rs

456
src/error.rs
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// Copyright 2014 The Rust Project Developers. See the COPYRIGHT
// file at the top-level directory of this distribution and at
// http://rust-lang.org/COPYRIGHT.
//
// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
// option. This file may not be copied, modified, or distributed
// except according to those terms.
//! Traits for working with Errors.
//!
//! # The `Error` trait
//!
//! `Error` is a trait representing the basic expectations for error values,
//! i.e. values of type `E` in [`Result<T, E>`]. At a minimum, errors must provide
//! a description, but they may optionally provide additional detail (via
//! [`Display`]) and cause chain information:
//!
//! ```
//! use std::fmt::Display;
//!
//! trait Error: Display {
//! fn description(&self) -> &str;
//!
//! fn cause(&self) -> Option<&Error> { None }
//! }
//! ```
//!
//! The [`cause`] method is generally used when errors cross "abstraction
//! boundaries", i.e. when a one module must report an error that is "caused"
//! by an error from a lower-level module. This setup makes it possible for the
//! high-level module to provide its own errors that do not commit to any
//! particular implementation, but also reveal some of its implementation for
//! debugging via [`cause`] chains.
//!
//! [`Result<T, E>`]: ../result/enum.Result.html
//! [`Display`]: ../fmt/trait.Display.html
//! [`cause`]: trait.Error.html#method.cause
// A note about crates and the facade:
//
// Originally, the `Error` trait was defined in libcore, and the impls
// were scattered about. However, coherence objected to this
// arrangement, because to create the blanket impls for `Box` required
// knowing that `&str: !Error`, and we have no means to deal with that
// sort of conflict just now. Therefore, for the time being, we have
// moved the `Error` trait into libstd. As we evolve a sol'n to the
// coherence challenge (e.g., specialization, neg impls, etc) we can
// reconsider what crate these items belong in.
use core::any::TypeId;
use core::cell;
use rustc_unicode::char;
use core::fmt::{self, Debug, Display};
use core::marker::Reflect;
use core::mem::transmute;
use core::num;
use core::str;
use collections::string::{self, String};
use alloc::boxed::Box;
/// Base functionality for all errors in Rust.
pub trait Error: Debug + Display + Reflect {
/// A short description of the error.
///
/// The description should not contain newlines or sentence-ending
/// punctuation, to facilitate embedding in larger user-facing
/// strings.
///
/// # Examples
///
/// ```
/// use std::error::Error;
///
/// match "xc".parse::<u32>() {
/// Err(e) => {
/// println!("Error: {}", e.description());
/// }
/// _ => println!("No error"),
/// }
/// ```
fn description(&self) -> &str;
/// 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 description(&self) -> &str {
/// "I'm the superhero of errors!"
/// }
///
/// fn cause(&self) -> Option<&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 description(&self) -> &str {
/// "I'm SuperError side kick!"
/// }
/// }
///
/// 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"),
/// }
/// }
/// ```
fn cause(&self) -> Option<&Error> { None }
/// Get the `TypeId` of `self`
#[doc(hidden)]
fn type_id(&self) -> TypeId where Self: 'static {
TypeId::of::<Self>()
}
}
impl<'a, E: Error + 'a> From<E> for Box<Error + 'a> {
fn from(err: E) -> Box<Error + 'a> {
Box::new(err)
}
}
impl<'a, E: Error + Send + Sync + 'a> From<E> for Box<Error + Send + Sync + 'a> {
fn from(err: E) -> Box<Error + Send + Sync + 'a> {
Box::new(err)
}
}
impl From<String> for Box<Error + Send + Sync> {
fn from(err: String) -> Box<Error + Send + Sync> {
#[derive(Debug)]
struct StringError(String);
impl Error for StringError {
fn description(&self) -> &str { &self.0 }
}
impl Display for StringError {
fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
Display::fmt(&self.0, f)
}
}
Box::new(StringError(err))
}
}
impl From<String> for Box<Error> {
fn from(str_err: String) -> Box<Error> {
let err1: Box<Error + Send + Sync> = From::from(str_err);
let err2: Box<Error> = err1;
err2
}
}
impl<'a, 'b> From<&'b str> for Box<Error + Send + Sync + 'a> {
fn from(err: &'b str) -> Box<Error + Send + Sync + 'a> {
From::from(String::from(err))
}
}
impl<'a> From<&'a str> for Box<Error> {
fn from(err: &'a str) -> Box<Error> {
From::from(String::from(err))
}
}
impl Error for str::ParseBoolError {
fn description(&self) -> &str { "failed to parse bool" }
}
impl Error for str::Utf8Error {
fn description(&self) -> &str {
"invalid utf-8: corrupt contents"
}
}
impl Error for num::ParseIntError {
fn description(&self) -> &str {
self.__description()
}
}
impl Error for num::TryFromIntError {
fn description(&self) -> &str {
self.__description()
}
}
impl Error for num::ParseFloatError {
fn description(&self) -> &str {
self.__description()
}
}
impl Error for string::FromUtf8Error {
fn description(&self) -> &str {
"invalid utf-8"
}
}
impl Error for string::FromUtf16Error {
fn description(&self) -> &str {
"invalid utf-16"
}
}
impl Error for string::ParseError {
fn description(&self) -> &str {
match *self {}
}
}
impl Error for char::DecodeUtf16Error {
fn description(&self) -> &str {
"unpaired surrogate found"
}
}
impl<T: Error> Error for Box<T> {
fn description(&self) -> &str {
Error::description(&**self)
}
fn cause(&self) -> Option<&Error> {
Error::cause(&**self)
}
}
impl Error for fmt::Error {
fn description(&self) -> &str {
"an error occurred when formatting an argument"
}
}
impl Error for cell::BorrowError {
fn description(&self) -> &str {
"already mutably borrowed"
}
}
impl Error for cell::BorrowMutError {
fn description(&self) -> &str {
"already borrowed"
}
}
impl Error for char::CharTryFromError {
fn description(&self) -> &str {
"converted integer out of range for `char`"
}
}
// copied from any.rs
impl Error + 'static {
/// Returns true if the boxed type is the same as `T`
#[inline]
pub fn is<T: Error + 'static>(&self) -> bool {
// Get TypeId of the type this function is instantiated with
let t = TypeId::of::<T>();
// Get TypeId of the type in the trait object
let boxed = self.type_id();
// Compare both TypeIds on equality
t == boxed
}
/// Returns some reference to the boxed value if it is of type `T`, or
/// `None` if it isn't.
#[inline]
pub fn downcast_ref<T: Error + 'static>(&self) -> Option<&T> {
if self.is::<T>() {
unsafe {
Some(&*(self as *const Error as *const T))
}
} else {
None
}
}
/// Returns some mutable reference to the boxed value if it is of type `T`, or
/// `None` if it isn't.
#[inline]
pub fn downcast_mut<T: Error + 'static>(&mut self) -> Option<&mut T> {
if self.is::<T>() {
unsafe {
Some(&mut *(self as *mut Error as *mut T))
}
} else {
None
}
}
}
impl Error + 'static + Send {
/// Forwards to the method defined on the type `Any`.
#[inline]
pub fn is<T: Error + 'static>(&self) -> bool {
<Error + 'static>::is::<T>(self)
}
/// Forwards to the method defined on the type `Any`.
#[inline]
pub fn downcast_ref<T: Error + 'static>(&self) -> Option<&T> {
<Error + 'static>::downcast_ref::<T>(self)
}
/// Forwards to the method defined on the type `Any`.
#[inline]
pub fn downcast_mut<T: Error + 'static>(&mut self) -> Option<&mut T> {
<Error + 'static>::downcast_mut::<T>(self)
}
}
impl Error + 'static + Send + Sync {
/// Forwards to the method defined on the type `Any`.
#[inline]
pub fn is<T: Error + 'static>(&self) -> bool {
<Error + 'static>::is::<T>(self)
}
/// Forwards to the method defined on the type `Any`.
#[inline]
pub fn downcast_ref<T: Error + 'static>(&self) -> Option<&T> {
<Error + 'static>::downcast_ref::<T>(self)
}
/// Forwards to the method defined on the type `Any`.
#[inline]
pub fn downcast_mut<T: Error + 'static>(&mut self) -> Option<&mut T> {
<Error + 'static>::downcast_mut::<T>(self)
}
}
impl Error {
#[inline]
/// Attempt to downcast the box to a concrete type.
pub fn downcast<T: Error + 'static>(self: Box<Self>) -> Result<Box<T>, Box<Error>> {
if self.is::<T>() {
unsafe {
let raw: *mut Error = Box::into_raw(self);
Ok(Box::from_raw(raw as *mut T))
}
} else {
Err(self)
}
}
}
impl Error + Send {
#[inline]
/// Attempt to downcast the box to a concrete type.
pub fn downcast<T: Error + 'static>(self: Box<Self>)
-> Result<Box<T>, Box<Error + Send>> {
let err: Box<Error> = self;
<Error>::downcast(err).map_err(|s| unsafe {
// reapply the Send marker
transmute::<Box<Error>, Box<Error + Send>>(s)
})
}
}
impl Error + Send + Sync {
#[inline]
/// Attempt to downcast the box to a concrete type.
pub fn downcast<T: Error + 'static>(self: Box<Self>)
-> Result<Box<T>, Box<Self>> {
let err: Box<Error> = self;
<Error>::downcast(err).map_err(|s| unsafe {
// reapply the Send+Sync marker
transmute::<Box<Error>, Box<Error + Send + Sync>>(s)
})
}
}
#[cfg(test)]
mod tests {
use super::Error;
use core::fmt;
use alloc::boxed::Box;
#[derive(Debug, PartialEq)]
struct A;
#[derive(Debug, PartialEq)]
struct B;
impl fmt::Display for A {
fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
write!(f, "A")
}
}
impl fmt::Display for B {
fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
write!(f, "B")
}
}
impl Error for A {
fn description(&self) -> &str { "A-desc" }
}
impl Error for B {
fn description(&self) -> &str { "A-desc" }
}
#[test]
fn downcasting() {
let mut a = A;
let mut a = &mut a as &mut (Error + 'static);
assert_eq!(a.downcast_ref::<A>(), Some(&A));
assert_eq!(a.downcast_ref::<B>(), None);
assert_eq!(a.downcast_mut::<A>(), Some(&mut A));
assert_eq!(a.downcast_mut::<B>(), None);
let a: Box<Error> = Box::new(A);
match a.downcast::<B>() {
Ok(..) => panic!("expected error"),
Err(e) => assert_eq!(*e.downcast::<A>().unwrap(), A),
}
}
}

4
src/lib.rs
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@ -1,10 +1,13 @@ @@ -1,10 +1,13 @@
#![feature(alloc)]
#![feature(collections)]
#![feature(char_escape_debug)]
#![feature(int_error_internals)]
#![feature(lang_items)]
#![feature(question_mark)]
#![feature(reflect_marker)]
#![feature(slice_patterns)]
#![feature(str_internals)]
#![feature(try_from)]
#![feature(unicode)]
#![no_std]
@ -26,6 +29,7 @@ pub mod services; @@ -26,6 +29,7 @@ pub mod services;
pub mod sdmc;
pub mod ascii;
pub mod error;
pub mod ffi;
pub mod panic;
pub mod path;

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