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

1 files changed, 6 insertions, 2 deletions

diff --git a/src/libstd/sync/poison.rs b/src/libstd/sync/poison.rs
index e28c3c37b6f..c97fcf7cefb 100644
--- a/src/libstd/sync/poison.rs
+++ b/src/libstd/sync/poison.rs
@@ -53,6 +53,7 @@ pub struct Guard {
 /// is held. The precise semantics for when a lock is poisoned is documented on
 /// each lock, but once a lock is poisoned then all future acquisitions will
 /// return this error.
+#[derive(Show)]
 #[stable]
 pub struct PoisonError<T> {
     guard: T,
@@ -60,6 +61,7 @@ pub struct PoisonError<T> {
 
 /// An enumeration of possible errors which can occur while calling the
 /// `try_lock` method.
+#[derive(Show)]
 #[stable]
 pub enum TryLockError<T> {
     /// The lock could not be acquired because another task failed while holding
@@ -90,7 +92,8 @@ pub type LockResult<Guard> = Result<Guard, PoisonError<Guard>>;
 #[stable]
 pub type TryLockResult<Guard> = Result<Guard, TryLockError<Guard>>;
 
-impl<T> fmt::Show for PoisonError<T> {
+#[stable]
+impl<T> fmt::Display for PoisonError<T> {
     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
         self.description().fmt(f)
     }
@@ -130,7 +133,8 @@ impl<T> FromError<PoisonError<T>> for TryLockError<T> {
     }
 }
 
-impl<T> fmt::Show for TryLockError<T> {
+#[stable]
+impl<T> fmt::Display for TryLockError<T> {
     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
         self.description().fmt(f)
     }