1 files changed, 9 insertions, 1 deletions
diff --git a/src/libsyntax/util/rc_slice.rs b/src/libsyntax/util/rc_slice.rs
index 2d9fd7aa875..d6939d71129 100644
--- a/src/libsyntax/util/rc_slice.rs
+++ b/src/libsyntax/util/rc_slice.rs
@@ -9,7 +9,7 @@
 // except according to those terms.
 
 use std::fmt;
-use std::ops::Deref;
+use std::ops::{Deref, Range};
 use std::rc::Rc;
 
 use rustc_data_structures::stable_hasher::{StableHasher, StableHasherResult,
@@ -30,6 +30,14 @@ impl<T> RcSlice<T> {
             data: Rc::new(vec.into_boxed_slice()),
         }
     }
+
+    pub fn sub_slice(&self, range: Range<usize>) -> Self {
+        RcSlice {
+            data: self.data.clone(),
+            offset: self.offset + range.start as u32,
+            len: (range.end - range.start) as u32,
+        }
+    }
 }
 
 impl<T> Deref for RcSlice<T> {