3 files changed, 3 insertions, 16 deletions
diff --git a/src/libstd/collections/hash/map.rs b/src/libstd/collections/hash/map.rs
index 9e229a28279..276959b715d 100644
--- a/src/libstd/collections/hash/map.rs
+++ b/src/libstd/collections/hash/map.rs
@@ -1226,14 +1226,7 @@ impl<K, V, S> Debug for HashMap<K, V, S>
     where K: Eq + Hash + Debug, V: Debug, S: HashState
 {
     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
-        try!(write!(f, "{{"));
-
-        for (i, (k, v)) in self.iter().enumerate() {
-            if i != 0 { try!(write!(f, ", ")); }
-            try!(write!(f, "{:?}: {:?}", *k, *v));
-        }
-
-        write!(f, "}}")
+        self.iter().fold(f.debug_map(), |b, (k, v)| b.entry(k, v)).finish()
     }
 }
 
diff --git a/src/libstd/collections/hash/set.rs b/src/libstd/collections/hash/set.rs
index 34b905595b7..9a4b55af4d5 100644
--- a/src/libstd/collections/hash/set.rs
+++ b/src/libstd/collections/hash/set.rs
@@ -612,14 +612,7 @@ impl<T, S> fmt::Debug for HashSet<T, S>
           S: HashState
 {
     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
-        try!(write!(f, "{{"));
-
-        for (i, x) in self.iter().enumerate() {
-            if i != 0 { try!(write!(f, ", ")); }
-            try!(write!(f, "{:?}", *x));
-        }
-
-        write!(f, "}}")
+        self.iter().fold(f.debug_set(), |b, e| b.entry(e)).finish()
     }
 }
 
diff --git a/src/libstd/lib.rs b/src/libstd/lib.rs
index 5f5f2fed567..b7cb8f9ed50 100644
--- a/src/libstd/lib.rs
+++ b/src/libstd/lib.rs
@@ -128,6 +128,7 @@
 #![feature(into_cow)]
 #![feature(slice_patterns)]
 #![feature(std_misc)]
+#![feature(debug_builders)]
 #![cfg_attr(test, feature(test, rustc_private, std_misc))]
 
 // Don't link to std. We are std.