auto merge of #17753 : aturon/rust/error-interop, r=alexcrichton

This PR:

* Adds the error interoperation traits (`Error` and `FromError`) to a new module, `std::error`, as per [RFC 70](https://github.com/rust-lang/rfcs/blob/master/active/0070-error-chaining.md). Note that this module must live in `std` in order to refer to `String`.

    Note that, until multidispatch lands, the `FromError` trait cannot be
usefully implemented outside of the blanket impl given here.

* Incorporates `std::error::FromError` into the `try!` macro.

* Implements `Error` for most existing error enumerations.

Closes #17747

1 files changed, 2 insertions, 2 deletions

diff --git a/src/libcore/prelude.rs b/src/libcore/prelude.rs
index 64917fb2541..0d4979a3575 100644
--- a/src/libcore/prelude.rs
+++ b/src/libcore/prelude.rs
@@ -37,8 +37,6 @@ pub use ops::{Shl, Shr};
 pub use ops::{Index, IndexMut};
 pub use ops::{Slice, SliceMut};
 pub use ops::{Fn, FnMut, FnOnce};
-pub use option::{Option, Some, None};
-pub use result::{Result, Ok, Err};
 
 // Reexported functions
 pub use iter::range;
@@ -56,7 +54,9 @@ pub use iter::{OrdIterator, MutableDoubleEndedIterator, ExactSize};
 pub use num::{Num, NumCast, CheckedAdd, CheckedSub, CheckedMul};
 pub use num::{Signed, Unsigned, Float};
 pub use num::{Primitive, Int, ToPrimitive, FromPrimitive};
+pub use option::{Option, Some, None};
 pub use ptr::RawPtr;
+pub use result::{Result, Ok, Err};
 pub use str::{Str, StrSlice};
 pub use tuple::{Tuple1, Tuple2, Tuple3, Tuple4};
 pub use tuple::{Tuple5, Tuple6, Tuple7, Tuple8};