Collect the definition of the `Error` trait into `libstd` for now. This

sidesteps a coherence difficulty where `liballoc` had to prove that
`&str: !Error`, which didn't involve any local types.

4 files changed, 20 insertions, 94 deletions

diff --git a/src/libcore/error.rs b/src/libcore/error.rs
deleted file mode 100644
index 24035b7d9a8..00000000000
--- a/src/libcore/error.rs
+++ /dev/null
@@ -1,56 +0,0 @@
-// 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.
-
-#![stable(feature = "rust1", since = "1.0.0")]
-
-use prelude::*;
-use fmt::{Debug, Display};
-
-/// Base functionality for all errors in Rust.
-#[stable(feature = "rust1", since = "1.0.0")]
-pub trait Error: Debug + Display {
-    /// A short description of the error.
-    ///
-    /// The description should not contain newlines or sentence-ending
-    /// punctuation, to facilitate embedding in larger user-facing
-    /// strings.
-    #[stable(feature = "rust1", since = "1.0.0")]
-    fn description(&self) -> &str;
-
-    /// The lower-level cause of this error, if any.
-    #[stable(feature = "rust1", since = "1.0.0")]
-    fn cause(&self) -> Option<&Error> { None }
-}
diff --git a/src/libcore/lib.rs b/src/libcore/lib.rs
index 3a9af50fefb..2189e2c3ad1 100644
--- a/src/libcore/lib.rs
+++ b/src/libcore/lib.rs
@@ -147,7 +147,6 @@ pub mod slice;
 pub mod str;
 pub mod hash;
 pub mod fmt;
-pub mod error;
 
 #[doc(primitive = "bool")]
 mod bool {
diff --git a/src/libcore/num/mod.rs b/src/libcore/num/mod.rs
index a4829ed96b3..7daa1a9f420 100644
--- a/src/libcore/num/mod.rs
+++ b/src/libcore/num/mod.rs
@@ -20,7 +20,6 @@ use self::wrapping::{OverflowingOps, WrappingOps};
 use char::CharExt;
 use clone::Clone;
 use cmp::{PartialEq, Eq, PartialOrd, Ord};
-use error::Error;
 use fmt;
 use intrinsics;
 use iter::Iterator;
@@ -2948,16 +2947,9 @@ enum IntErrorKind {
     Underflow,
 }
 
-#[stable(feature = "rust1", since = "1.0.0")]
-impl fmt::Display for ParseIntError {
-    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
-        self.description().fmt(f)
-    }
-}
-
-#[stable(feature = "rust1", since = "1.0.0")]
-impl Error for ParseIntError {
-    fn description(&self) -> &str {
+impl ParseIntError {
+    #[unstable(feature = "core", reason = "available through Error trait")]
+    pub fn description(&self) -> &str {
         match self.kind {
             IntErrorKind::Empty => "cannot parse integer from empty string",
             IntErrorKind::InvalidDigit => "invalid digit found in string",
@@ -2967,6 +2959,13 @@ impl Error for ParseIntError {
     }
 }
 
+#[stable(feature = "rust1", since = "1.0.0")]
+impl fmt::Display for ParseIntError {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        self.description().fmt(f)
+    }
+}
+
 /// An error which can be returned when parsing a float.
 #[derive(Debug, Clone, PartialEq)]
 #[stable(feature = "rust1", since = "1.0.0")]
@@ -2978,19 +2977,19 @@ enum FloatErrorKind {
     Invalid,
 }
 
-#[stable(feature = "rust1", since = "1.0.0")]
-impl fmt::Display for ParseFloatError {
-    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
-        self.description().fmt(f)
-    }
-}
-
-#[stable(feature = "rust1", since = "1.0.0")]
-impl Error for ParseFloatError {
-    fn description(&self) -> &str {
+impl ParseFloatError {
+    #[unstable(feature = "core", reason = "available through Error trait")]
+    pub fn description(&self) -> &str {
         match self.kind {
             FloatErrorKind::Empty => "cannot parse float from empty string",
             FloatErrorKind::Invalid => "invalid float literal",
         }
     }
 }
+
+#[stable(feature = "rust1", since = "1.0.0")]
+impl fmt::Display for ParseFloatError {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        self.description().fmt(f)
+    }
+}
diff --git a/src/libcore/str/mod.rs b/src/libcore/str/mod.rs
index 934c4515614..4c366d32718 100644
--- a/src/libcore/str/mod.rs
+++ b/src/libcore/str/mod.rs
@@ -22,7 +22,6 @@ use char::CharExt;
 use clone::Clone;
 use cmp::{self, Eq};
 use default::Default;
-use error::Error;
 use fmt;
 use iter::ExactSizeIterator;
 use iter::{Map, Iterator, DoubleEndedIterator};
@@ -192,11 +191,6 @@ impl fmt::Display for ParseBoolError {
     }
 }
 
-#[stable(feature = "rust1", since = "1.0.0")]
-impl Error for ParseBoolError {
-    fn description(&self) -> &str { "failed to parse bool" }
-}
-
 /*
 Section: Creating a string
 */
@@ -242,16 +236,6 @@ pub unsafe fn from_utf8_unchecked<'a>(v: &'a [u8]) -> &'a str {
 }
 
 #[stable(feature = "rust1", since = "1.0.0")]
-impl Error for Utf8Error {
-    fn description(&self) -> &str {
-        match *self {
-            Utf8Error::TooShort => "invalid utf-8: not enough bytes",
-            Utf8Error::InvalidByte(..) => "invalid utf-8: corrupt contents",
-        }
-    }
-}
-
-#[stable(feature = "rust1", since = "1.0.0")]
 impl fmt::Display for Utf8Error {
     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
         match *self {