Add the DerefImm and DerefMut traits.

Author: eddyb

src/librustc/middle/lang_items.rs

@@ -232,6 +232,9 @@ lets_do_this! {
     ShrTraitLangItem,                "shr",                     shr_trait;
     IndexTraitLangItem,              "index",                   index_trait;
 
+    DerefTraitLangItem,              "deref",                   deref_trait;
+    DerefMutTraitLangItem,           "deref_mut",               deref_mut_trait;
+
     EqTraitLangItem,                 "eq",                      eq_trait;
     OrdTraitLangItem,                "ord",                     ord_trait;
 

src/libstd/ops.rs

@@ -464,6 +464,28 @@ pub trait Index<Index,Result> {
     fn index(&self, index: &Index) -> Result;
 }
 
+#[cfg(stage0)]
+pub trait Deref<Result> {
+    fn deref<'a>(&'a self) -> &'a Result;
+}
+
+#[cfg(not(stage0))]
+#[lang="deref"]
+pub trait Deref<Result> {
+    fn deref<'a>(&'a self) -> &'a Result;
+}
+
+#[cfg(stage0)]
+pub trait DerefMut<Result>: Deref<Result> {
+    fn deref_mut<'a>(&'a mut self) -> &'a mut Result;
+}
+
+#[cfg(not(stage0))]
+#[lang="deref_mut"]
+pub trait DerefMut<Result>: Deref<Result> {
+    fn deref_mut<'a>(&'a mut self) -> &'a mut Result;
+}
+
 #[cfg(test)]
 mod bench {
     extern crate test;

src/libstd/prelude.rs

@@ -23,7 +23,7 @@ generally useful to many Rust programs.
 pub use kinds::{Freeze, Pod, Send, Sized};
 pub use ops::{Add, Sub, Mul, Div, Rem, Neg, Not};
 pub use ops::{BitAnd, BitOr, BitXor};
-pub use ops::{Drop};
+pub use ops::{Drop, Deref, DerefMut};
 pub use ops::{Shl, Shr, Index};
 pub use option::{Option, Some, None};
 pub use result::{Result, Ok, Err};