std: Tweak String implementations

This commit performs a pass over the implementations of the new `String` trait
in the formatting module. Some implementations were removed as a conservative
move pending an upcoming convention about `String` implementations, and some
were added in order to retain consistency across the libraries. Specifically:

* All "smart pointers" implement `String` now, adding missing implementations
  for `Arc` and `Rc`.
* The `Vec<T>` and `[T]` types no longer implement `String`.
* The `*const T` and `*mut T` type no longer implement `String`.
* The `()` type no longer implements `String`.
* The `Path` type's `Show` implementation does not surround itself with `Path
  {}` (a minor tweak).

All implementations of `String` in this PR were also marked `#[stable]` to
indicate that the types will continue to implement the `String` trait regardless
of what it looks like.

1 files changed, 6 insertions, 6 deletions

diff --git a/src/libcore/option.rs b/src/libcore/option.rs
index 272570a0d5b..56e27e801af 100644
--- a/src/libcore/option.rs
+++ b/src/libcore/option.rs
@@ -145,17 +145,18 @@
 
 use self::Option::*;
 
+use clone::Clone;
 use cmp::{Eq, Ord};
 use default::Default;
-use iter::{Iterator, IteratorExt, DoubleEndedIterator, FromIterator};
+use fmt;
 use iter::{ExactSizeIterator};
+use iter::{Iterator, IteratorExt, DoubleEndedIterator, FromIterator};
 use mem;
-use result::Result;
+use ops::{Deref, FnOnce};
 use result::Result::{Ok, Err};
-use slice;
+use result::Result;
 use slice::AsSlice;
-use clone::Clone;
-use ops::{Deref, FnOnce};
+use slice;
 
 // Note that this is not a lang item per se, but it has a hidden dependency on
 // `Iterator`, which is one. The compiler assumes that the `next` method of
@@ -762,7 +763,6 @@ impl<T> AsSlice<T> for Option<T> {
 
 #[stable]
 impl<T> Default for Option<T> {
-    #[stable]
     #[inline]
     #[stable]
     fn default() -> Option<T> { None }