core: Derive Show impls wherever possible

These were temporarily moved to explicit implementations, but now that fmt is in
core it's possible to derive again.

Author: alexcrichton

src/libcore/cmp.rs

@@ -82,7 +82,7 @@ pub trait TotalEq: Eq {
 }
 
 /// An ordering is, e.g, a result of a comparison between two values.
-#[deriving(Clone, Eq)]
+#[deriving(Clone, Eq, Show)]
 pub enum Ordering {
    /// An ordering where a compared value is less [than another].
    Less = -1,

src/libcore/intrinsics.rs

@@ -471,7 +471,7 @@ extern "rust-intrinsic" {
 /// `TypeId` represents a globally unique identifier for a type
 #[lang="type_id"] // This needs to be kept in lockstep with the code in trans/intrinsic.rs and
                   // middle/lang_items.rs
-#[deriving(Eq, TotalEq)]
+#[deriving(Eq, TotalEq, Show)]
 #[cfg(not(test))]
 pub struct TypeId {
     t: u64,

src/libcore/iter.rs

@@ -969,7 +969,7 @@ impl<A: TotalOrd, T: Iterator<A>> OrdIterator<A> for T {
 }
 
 /// `MinMaxResult` is an enum returned by `min_max`. See `OrdIterator::min_max` for more detail.
-#[deriving(Clone, Eq)]
+#[deriving(Clone, Eq, Show)]
 pub enum MinMaxResult<T> {
     /// Empty iterator
     NoElements,

src/libcore/option.rs

@@ -148,7 +148,7 @@ use mem;
 use slice;
 
 /// The `Option`
-#[deriving(Clone, Eq, Ord, TotalEq, TotalOrd)]
+#[deriving(Clone, Eq, Ord, TotalEq, TotalOrd, Show)]
 pub enum Option<T> {
     /// No value
     None,

src/libcore/result.rs

@@ -275,7 +275,7 @@ use option::{None, Option, Some};
 /// `Result` is a type that represents either success (`Ok`) or failure (`Err`).
 ///
 /// See the [`std::result`](index.html) module documentation for details.
-#[deriving(Clone, Eq, Ord, TotalEq, TotalOrd)]
+#[deriving(Clone, Eq, Ord, TotalEq, TotalOrd, Show)]
 #[must_use]
 pub enum Result<T, E> {
     /// Contains the success value

src/libcore/str.rs

@@ -542,7 +542,7 @@ pub struct UTF16Items<'a> {
     iter: slice::Items<'a, u16>
 }
 /// The possibilities for values decoded from a `u16` stream.
-#[deriving(Eq, TotalEq, Clone)]
+#[deriving(Eq, TotalEq, Clone, Show)]
 pub enum UTF16Item {
     /// A valid codepoint.
     ScalarValue(char),