2 files changed, 31 insertions, 0 deletions
diff --git a/src/libsyntax/parse/token.rs b/src/libsyntax/parse/token.rs
index cf05a4375a8..b94b53076ec 100644
--- a/src/libsyntax/parse/token.rs
+++ b/src/libsyntax/parse/token.rs
@@ -18,9 +18,11 @@ use util::interner;
 
 use core::cast;
 use core::char;
+use core::cmp::Equiv;
 use core::hashmap::HashSet;
 use core::str;
 use core::task;
+use core::to_bytes;
 
 #[auto_encode]
 #[auto_decode]
@@ -355,6 +357,19 @@ pub mod special_idents {
     pub static type_self: ident = ident { repr: 36u, ctxt: 0};    // `Self`
 }
 
+pub struct StringRef<'self>(&'self str);
+
+impl<'self> Equiv<@~str> for StringRef<'self> {
+    #[inline(always)]
+    fn equiv(&self, other: &@~str) -> bool { str::eq_slice(**self, **other) }
+}
+
+impl<'self> to_bytes::IterBytes for StringRef<'self> {
+    fn iter_bytes(&self, lsb0: bool, f: to_bytes::Cb) {
+        (**self).iter_bytes(lsb0, f);
+    }
+}
+
 pub struct ident_interner {
     priv interner: Interner<@~str>,
 }
@@ -372,6 +387,13 @@ pub impl ident_interner {
     fn len(&self) -> uint {
         self.interner.len()
     }
+    fn find_equiv<Q:Hash + IterBytes + Equiv<@~str>>(&self, val: &Q)
+                                                  -> Option<ast::ident> {
+        match self.interner.find_equiv(val) {
+            Some(v) => Some(ast::ident { repr: v }),
+            None => None,
+        }
+    }
 }
 
 pub fn mk_ident_interner() -> @ident_interner {
diff --git a/src/libsyntax/util/interner.rs b/src/libsyntax/util/interner.rs
index 75bcac1b163..cda1c6c0df3 100644
--- a/src/libsyntax/util/interner.rs
+++ b/src/libsyntax/util/interner.rs
@@ -16,6 +16,7 @@
 #[macro_escape];
 
 use core::prelude::*;
+use core::cmp::Equiv;
 use core::hashmap::HashMap;
 
 pub struct Interner<T> {
@@ -67,6 +68,14 @@ pub impl<T:Eq + IterBytes + Hash + Const + Copy> Interner<T> {
     fn get(&self, idx: uint) -> T { self.vect[idx] }
 
     fn len(&self) -> uint { let vect = &*self.vect; vect.len() }
+
+    fn find_equiv<Q:Hash + IterBytes + Equiv<T>>(&self, val: &Q)
+                                              -> Option<uint> {
+        match self.map.find_equiv(val) {
+            Some(v) => Some(*v),
+            None => None,
+        }
+    }
 }
 
 /* Key for thread-local data for sneaking interner information to the