std: Rename Show/String to Debug/Display

This commit is an implementation of [RFC 565][rfc] which is a stabilization of
the `std::fmt` module and the implementations of various formatting traits.
Specifically, the following changes were performed:

[rfc]: https://github.com/rust-lang/rfcs/blob/master/text/0565-show-string-guidelines.md

* The `Show` trait is now deprecated, it was renamed to `Debug`
* The `String` trait is now deprecated, it was renamed to `Display`
* Many `Debug` and `Display` implementations were audited in accordance with the
  RFC and audited implementations now have the `#[stable]` attribute
  * Integers and floats no longer print a suffix
  * Smart pointers no longer print details that they are a smart pointer
  * Paths with `Debug` are now quoted and escape characters
* The `unwrap` methods on `Result` now require `Display` instead of `Debug`
* The `Error` trait no longer has a `detail` method and now requires that
  `Display` must be implemented. With the loss of `String`, this has moved into
  libcore.
* `impl<E: Error> FromError<E> for Box<Error>` now exists
* `derive(Show)` has been renamed to `derive(Debug)`. This is not currently
  warned about due to warnings being emitted on stage1+

While backwards compatibility is attempted to be maintained with a blanket
implementation of `Display` for the old `String` trait (and the same for
`Show`/`Debug`) this is still a breaking change due to primitives no longer
implementing `String` as well as modifications such as `unwrap` and the `Error`
trait. Most code is fairly straightforward to update with a rename or tweaks of
method calls.

[breaking-change]
Closes #21436

src/libcollections/string.rs

@@ -18,6 +18,7 @@ use core::prelude::*;
 
 use core::borrow::{Cow, IntoCow};
 use core::default::Default;
+use core::error::Error;
 use core::fmt;
 use core::hash;
 use core::iter::FromIterator;
@@ -40,6 +41,7 @@ pub struct String {
 
 /// A possible error value from the `String::from_utf8` function.
 #[stable]
+#[derive(Show)]
 pub struct FromUtf8Error {
     bytes: Vec<u8>,
     error: Utf8Error,
@@ -48,6 +50,7 @@ pub struct FromUtf8Error {
 /// A possible error value from the `String::from_utf16` function.
 #[stable]
 #[allow(missing_copy_implementations)]
+#[derive(Show)]
 pub struct FromUtf16Error(());
 
 impl String {
@@ -680,30 +683,28 @@ impl FromUtf8Error {
     pub fn utf8_error(&self) -> Utf8Error { self.error }
 }
 
-impl fmt::Show for FromUtf8Error {
+#[stable]
+impl fmt::Display for FromUtf8Error {
     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
-        fmt::String::fmt(self, f)
+        fmt::Display::fmt(&self.error, f)
     }
 }
 
 #[stable]
-impl fmt::String for FromUtf8Error {
-    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
-        fmt::String::fmt(&self.error, f)
-    }
+impl Error for FromUtf8Error {
+    fn description(&self) -> &str { "invalid utf-8" }
 }
 
-impl fmt::Show for FromUtf16Error {
+#[stable]
+impl fmt::Display for FromUtf16Error {
     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
-        fmt::String::fmt(self, f)
+        fmt::Display::fmt("invalid utf-16: lone surrogate found", f)
     }
 }
 
 #[stable]
-impl fmt::String for FromUtf16Error {
-    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
-        fmt::String::fmt("invalid utf-16: lone surrogate found", f)
-    }
+impl Error for FromUtf16Error {
+    fn description(&self) -> &str { "invalid utf-16" }
 }
 
 #[stable]
@@ -814,18 +815,18 @@ impl Default for String {
 }
 
 #[stable]
-impl fmt::String for String {
+impl fmt::Display for String {
     #[inline]
     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
-        fmt::String::fmt(&**self, f)
+        fmt::Display::fmt(&**self, f)
     }
 }
 
-#[unstable = "waiting on fmt stabilization"]
-impl fmt::Show for String {
+#[stable]
+impl fmt::Debug for String {
     #[inline]
     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
-        fmt::Show::fmt(&**self, f)
+        fmt::Debug::fmt(&**self, f)
     }
 }
 
@@ -934,7 +935,7 @@ pub trait ToString {
     fn to_string(&self) -> String;
 }
 
-impl<T: fmt::String + ?Sized> ToString for T {
+impl<T: fmt::Display + ?Sized> ToString for T {
     #[inline]
     fn to_string(&self) -> String {
         use core::fmt::Writer;
@@ -1295,10 +1296,10 @@ mod tests {
     fn test_vectors() {
         let x: Vec<int> = vec![];
         assert_eq!(format!("{:?}", x), "[]");
-        assert_eq!(format!("{:?}", vec![1i]), "[1i]");
-        assert_eq!(format!("{:?}", vec![1i, 2, 3]), "[1i, 2i, 3i]");
+        assert_eq!(format!("{:?}", vec![1i]), "[1]");
+        assert_eq!(format!("{:?}", vec![1i, 2, 3]), "[1, 2, 3]");
         assert!(format!("{:?}", vec![vec![], vec![1i], vec![1i, 1]]) ==
-               "[[], [1i], [1i, 1i]]");
+               "[[], [1], [1, 1]]");
     }
 
     #[test]