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

3 files changed, 31 insertions, 21 deletions

diff --git a/src/liballoc/arc.rs b/src/liballoc/arc.rs
index c0cd034abfa..5f8cd6baf9a 100644
--- a/src/liballoc/arc.rs
+++ b/src/liballoc/arc.rs
@@ -72,7 +72,7 @@ use core::prelude::*;
 use core::atomic;
 use core::atomic::Ordering::{Relaxed, Release, Acquire, SeqCst};
 use core::borrow::BorrowFrom;
-use core::fmt::{self, Show};
+use core::fmt;
 use core::cmp::{Ordering};
 use core::default::Default;
 use core::mem::{min_align_of, size_of};
@@ -578,16 +578,17 @@ impl<T: Ord> Ord for Arc<T> {
 #[stable]
 impl<T: Eq> Eq for Arc<T> {}
 
-impl<T: fmt::Show> fmt::Show for Arc<T> {
+#[stable]
+impl<T: fmt::Display> fmt::Display for Arc<T> {
     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
-        write!(f, "Arc({:?})", (**self))
+        fmt::Display::fmt(&**self, f)
     }
 }
 
 #[stable]
-impl<T: fmt::String> fmt::String for Arc<T> {
+impl<T: fmt::Debug> fmt::Debug for Arc<T> {
     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
-        fmt::String::fmt(&**self, f)
+        fmt::Debug::fmt(&**self, f)
     }
 }
 
@@ -806,7 +807,7 @@ mod tests {
     #[test]
     fn show_arc() {
         let a = Arc::new(5u32);
-        assert!(format!("{:?}", a) == "Arc(5u32)")
+        assert_eq!(format!("{:?}", a), "5");
     }
 
     // Make sure deriving works with Arc<T>
diff --git a/src/liballoc/boxed.rs b/src/liballoc/boxed.rs
index a2cc98c7d01..c2ee1a5d024 100644
--- a/src/liballoc/boxed.rs
+++ b/src/liballoc/boxed.rs
@@ -16,16 +16,17 @@ use core::any::Any;
 use core::clone::Clone;
 use core::cmp::{PartialEq, PartialOrd, Eq, Ord, Ordering};
 use core::default::Default;
+use core::error::{Error, FromError};
 use core::fmt;
 use core::hash::{self, Hash};
 use core::marker::Sized;
 use core::mem;
+use core::ops::{Deref, DerefMut};
 use core::option::Option;
 use core::ptr::Unique;
 use core::raw::TraitObject;
-use core::result::Result;
 use core::result::Result::{Ok, Err};
-use core::ops::{Deref, DerefMut};
+use core::result::Result;
 
 /// A value that represents the global exchange heap. This is the default
 /// place that the `box` keyword allocates into when no place is supplied.
@@ -156,20 +157,22 @@ impl BoxAny for Box<Any> {
     }
 }
 
-impl<T: ?Sized + fmt::Show> fmt::Show for Box<T> {
+#[stable]
+impl<T: fmt::Display + ?Sized> fmt::Display for Box<T> {
     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
-        write!(f, "Box({:?})", &**self)
+        fmt::Display::fmt(&**self, f)
     }
 }
 
 #[stable]
-impl<T: ?Sized + fmt::String> fmt::String for Box<T> {
+impl<T: fmt::Debug + ?Sized> fmt::Debug for Box<T> {
     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
-        fmt::String::fmt(&**self, f)
+        fmt::Debug::fmt(&**self, f)
     }
 }
 
-impl fmt::Show for Box<Any> {
+#[stable]
+impl fmt::Debug for Box<Any> {
     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
         f.pad("Box<Any>")
     }
@@ -187,6 +190,12 @@ impl<T: ?Sized> DerefMut for Box<T> {
     fn deref_mut(&mut self) -> &mut T { &mut **self }
 }
 
+impl<'a, E: Error + 'a> FromError<E> for Box<Error + 'a> {
+    fn from_error(err: E) -> Box<Error + 'a> {
+        Box::new(err)
+    }
+}
+
 #[cfg(test)]
 mod test {
     #[test]
diff --git a/src/liballoc/rc.rs b/src/liballoc/rc.rs
index 7191a7af346..9a4221699b1 100644
--- a/src/liballoc/rc.rs
+++ b/src/liballoc/rc.rs
@@ -693,17 +693,17 @@ impl<S: hash::Hasher, T: Hash<S>> Hash<S> for Rc<T> {
     }
 }
 
-#[unstable = "Show is experimental."]
-impl<T: fmt::Show> fmt::Show for Rc<T> {
+#[stable]
+impl<T: fmt::Display> fmt::Display for Rc<T> {
     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
-        write!(f, "Rc({:?})", **self)
+        fmt::Display::fmt(&**self, f)
     }
 }
 
 #[stable]
-impl<T: fmt::String> fmt::String for Rc<T> {
+impl<T: fmt::Debug> fmt::Debug for Rc<T> {
     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
-        fmt::String::fmt(&**self, f)
+        fmt::Debug::fmt(&**self, f)
     }
 }
 
@@ -890,8 +890,8 @@ impl<T> Clone for Weak<T> {
     }
 }
 
-#[unstable = "Show is experimental."]
-impl<T: fmt::Show> fmt::Show for Weak<T> {
+#[stable]
+impl<T: fmt::Debug> fmt::Debug for Weak<T> {
     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
         write!(f, "(Weak)")
     }
@@ -1134,7 +1134,7 @@ mod tests {
     #[test]
     fn test_show() {
         let foo = Rc::new(75u);
-        assert!(format!("{:?}", foo) == "Rc(75u)")
+        assert_eq!(format!("{:?}", foo), "75");
     }
 
 }