1 files changed, 6 insertions, 0 deletions
diff --git a/src/librustc_data_structures/indexed_vec.rs b/src/librustc_data_structures/indexed_vec.rs
index b3918f1e4bc..91234631499 100644
--- a/src/librustc_data_structures/indexed_vec.rs
+++ b/src/librustc_data_structures/indexed_vec.rs
@@ -15,6 +15,7 @@ use std::marker::PhantomData;
 use std::ops::{Index, IndexMut, Range};
 use std::fmt;
 use std::vec;
+use std::u32;
 
 use rustc_serialize as serialize;
 
@@ -31,6 +32,11 @@ impl Idx for usize {
     fn index(self) -> usize { self }
 }
 
+impl Idx for u32 {
+    fn new(idx: usize) -> Self { assert!(idx <= u32::MAX as usize); idx as u32 }
+    fn index(self) -> usize { self as usize }
+}
+
 #[derive(Clone)]
 pub struct IndexVec<I: Idx, T> {
     pub raw: Vec<T>,