std: Stabilize last bits of io::Error

This commit stabilizes a few remaining bits of the `io::Error` type:

* The `Error::new` method is now stable. The last `detail` parameter was removed
  and the second `desc` parameter was generalized to `E: Into<Box<Error>>` to
  allow creating an I/O error from any form of error. Currently there is no form
  of downcasting, but this will be added in time.

* An implementation of `From<&str> for Box<Error>` was added to liballoc to
  allow construction of errors from raw strings.

* The `Error::raw_os_error` method was stabilized as-is.

* Trait impls for `Clone`, `Eq`, and `PartialEq` were removed from `Error` as it
  is not possible to use them with trait objects.

This is a breaking change due to the modification of the `new` method as well as
the removal of the trait implementations for the `Error` type.

[breaking-change]

1 files changed, 3 insertions, 2 deletions

diff --git a/src/librustc_back/target/apple_ios_base.rs b/src/librustc_back/target/apple_ios_base.rs
index 2fbbe7d1f7c..42cbdd7577d 100644
--- a/src/librustc_back/target/apple_ios_base.rs
+++ b/src/librustc_back/target/apple_ios_base.rs
@@ -47,9 +47,10 @@ pub fn get_sdk_root(sdk_name: &str) -> String {
                               Ok(String::from_utf8(output.stdout).unwrap())
                           } else {
                               let error = String::from_utf8(output.stderr);
+                              let error = format!("process exit with error: {}",
+                                                  error.unwrap());
                               Err(io::Error::new(io::ErrorKind::Other,
-                                                 "process exit with error",
-                                                 error.ok()))
+                                                 &error[..]))
                           }
                       });