diff --git a/compiler/rustc_serialize/src/serialize.rs b/compiler/rustc_serialize/src/serialize.rs
index bae5f259fcc..db8555edd0f 100644
--- a/compiler/rustc_serialize/src/serialize.rs
+++ b/compiler/rustc_serialize/src/serialize.rs
@@ -288,7 +288,7 @@ fn decode(d: &mut D) -> Rc<T> {
 impl<S: Encoder, T: Encodable<S>> Encodable<S> for [T] {
     default fn encode(&self, s: &mut S) {
         s.emit_usize(self.len());
-        for e in self.iter() {
+        for e in self {
             e.encode(s);
         }
     }
@@ -527,7 +527,7 @@ fn decode(d: &mut D) -> ThinVec<T> {
 impl<S: Encoder, T: Encodable<S>> Encodable<S> for VecDeque<T> {
     fn encode(&self, s: &mut S) {
         s.emit_usize(self.len());
-        for e in self.iter() {
+        for e in self {
             e.encode(s);
         }
     }
@@ -547,7 +547,7 @@ impl<S: Encoder, K, V> Encodable<S> for BTreeMap<K, V>
 {
     fn encode(&self, e: &mut S) {
         e.emit_usize(self.len());
-        for (key, val) in self.iter() {
+        for (key, val) in self {
             key.encode(e);
             val.encode(e);
         }
@@ -571,7 +571,7 @@ impl<S: Encoder, T> Encodable<S> for BTreeSet<T>
 {
     fn encode(&self, s: &mut S) {
         s.emit_usize(self.len());
-        for e in self.iter() {
+        for e in self {
             e.encode(s);
         }
     }
@@ -595,7 +595,7 @@ impl<E: Encoder, K, V, S> Encodable<E> for HashMap<K, V, S>
 {
     fn encode(&self, e: &mut E) {
         e.emit_usize(self.len());
-        for (key, val) in self.iter() {
+        for (key, val) in self {
             key.encode(e);
             val.encode(e);
         }
@@ -621,7 +621,7 @@ impl<E: Encoder, T, S> Encodable<E> for HashSet<T, S>
 {
     fn encode(&self, s: &mut E) {
         s.emit_usize(self.len());
-        for e in self.iter() {
+        for e in self {
             e.encode(s);
         }
     }
@@ -646,7 +646,7 @@ impl<E: Encoder, K, V, S> Encodable<E> for indexmap::IndexMap<K, V, S>
 {
     fn encode(&self, e: &mut E) {
         e.emit_usize(self.len());
-        for (key, val) in self.iter() {
+        for (key, val) in self {
             key.encode(e);
             val.encode(e);
         }
@@ -672,7 +672,7 @@ impl<E: Encoder, T, S> Encodable<E> for indexmap::IndexSet<T, S>
 {
     fn encode(&self, s: &mut E) {
         s.emit_usize(self.len());
-        for e in self.iter() {
+        for e in self {
             e.encode(s);
         }
     }