rollup merge of #23879: seanmonstar/del-from-error

Conflicts:
	src/libcore/error.rs

src/libcore/convert.rs

@@ -95,6 +95,13 @@ impl<'a, T: ?Sized, U: ?Sized> AsMut<U> for &'a mut T where T: AsMut<U> {
 //     }
 // }
 
+// From itself is always itself
+impl<T> From<T> for T {
+    fn from(t: T) -> T {
+        t
+    }
+}
+
 // From implies Into
 #[stable(feature = "rust1", since = "1.0.0")]
 impl<T, U> Into<U> for T where U: From<T> {

src/libcore/error.rs

@@ -33,49 +33,6 @@
 //! 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.
-//!
-//! # The `FromError` trait
-//!
-//! `FromError` is a simple trait that expresses conversions between different
-//! error types. To provide maximum flexibility, it does not require either of
-//! the types to actually implement the `Error` trait, although this will be the
-//! common case.
-//!
-//! The main use of this trait is in the `try!` macro, which uses it to
-//! automatically convert a given error to the error specified in a function's
-//! return type.
-//!
-//! For example,
-//!
-//! ```
-//! #![feature(core)]
-//! use std::error::FromError;
-//! use std::{io, str};
-//! use std::fs::File;
-//!
-//! enum MyError {
-//!     Io(io::Error),
-//!     Utf8(str::Utf8Error),
-//! }
-//!
-//! impl FromError<io::Error> for MyError {
-//!     fn from_error(err: io::Error) -> MyError { MyError::Io(err) }
-//! }
-//!
-//! impl FromError<str::Utf8Error> for MyError {
-//!     fn from_error(err: str::Utf8Error) -> MyError { MyError::Utf8(err) }
-//! }
-//!
-//! #[allow(unused_variables)]
-//! fn open_and_map() -> Result<(), MyError> {
-//!     let b = b"foo.txt";
-//!     let s = try!(str::from_utf8(b));
-//!     let f = try!(File::open(s));
-//!
-//!     // do something interesting here...
-//!     Ok(())
-//! }
-//! ```
 
 #![stable(feature = "rust1", since = "1.0.0")]
 
@@ -97,19 +54,3 @@ pub trait Error: Debug + Display {
     #[stable(feature = "rust1", since = "1.0.0")]
     fn cause(&self) -> Option<&Error> { None }
 }
-
-/// A trait for types that can be converted from a given error type `E`.
-#[stable(feature = "rust1", since = "1.0.0")]
-pub trait FromError<E> {
-    /// Perform the conversion.
-    #[stable(feature = "rust1", since = "1.0.0")]
-    fn from_error(err: E) -> Self;
-}
-
-// Any type is convertable from itself
-#[stable(feature = "rust1", since = "1.0.0")]
-impl<E> FromError<E> for E {
-    fn from_error(err: E) -> E {
-        err
-    }
-}

src/libcore/macros.rs

@@ -156,7 +156,7 @@ macro_rules! debug_assert_eq {
 
 /// Short circuiting evaluation on Err
 ///
-/// `libstd` contains a more general `try!` macro that uses `FromError`.
+/// `libstd` contains a more general `try!` macro that uses `From<E>`.
 #[macro_export]
 macro_rules! try {
     ($e:expr) => ({