diff --git a/compiler/rustc_serialize/src/collection_impls.rs b/compiler/rustc_serialize/src/collection_impls.rs
deleted file mode 100644
index b7512593c14..00000000000
--- a/compiler/rustc_serialize/src/collection_impls.rs
+++ /dev/null
@@ -1,263 +0,0 @@
-//! Implementations of serialization for structures found in liballoc
-
-use crate::{Decodable, Decoder, Encodable, Encoder};
-use smallvec::{Array, SmallVec};
-use std::collections::{BTreeMap, BTreeSet, HashMap, HashSet, VecDeque};
-use std::hash::{BuildHasher, Hash};
-use std::rc::Rc;
-use std::sync::Arc;
-use thin_vec::ThinVec;
-
-impl<S: Encoder, A: Array<Item: Encodable<S>>> Encodable<S> for SmallVec<A> {
-    fn encode(&self, s: &mut S) {
-        let slice: &[A::Item] = self;
-        slice.encode(s);
-    }
-}
-
-impl<D: Decoder, A: Array<Item: Decodable<D>>> Decodable<D> for SmallVec<A> {
-    fn decode(d: &mut D) -> SmallVec<A> {
-        let len = d.read_usize();
-        (0..len).map(|_| Decodable::decode(d)).collect()
-    }
-}
-
-impl<S: Encoder, T: Encodable<S>> Encodable<S> for ThinVec<T> {
-    fn encode(&self, s: &mut S) {
-        self.as_slice().encode(s);
-    }
-}
-
-impl<D: Decoder, T: Decodable<D>> Decodable<D> for ThinVec<T> {
-    fn decode(d: &mut D) -> ThinVec<T> {
-        let len = d.read_usize();
-        (0..len).map(|_| Decodable::decode(d)).collect()
-    }
-}
-
-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() {
-            e.encode(s);
-        }
-    }
-}
-
-impl<D: Decoder, T: Decodable<D>> Decodable<D> for VecDeque<T> {
-    fn decode(d: &mut D) -> VecDeque<T> {
-        let len = d.read_usize();
-        (0..len).map(|_| Decodable::decode(d)).collect()
-    }
-}
-
-impl<S: Encoder, K, V> Encodable<S> for BTreeMap<K, V>
-where
-    K: Encodable<S> + PartialEq + Ord,
-    V: Encodable<S>,
-{
-    fn encode(&self, e: &mut S) {
-        e.emit_usize(self.len());
-        for (key, val) in self.iter() {
-            key.encode(e);
-            val.encode(e);
-        }
-    }
-}
-
-impl<D: Decoder, K, V> Decodable<D> for BTreeMap<K, V>
-where
-    K: Decodable<D> + PartialEq + Ord,
-    V: Decodable<D>,
-{
-    fn decode(d: &mut D) -> BTreeMap<K, V> {
-        let len = d.read_usize();
-        let mut map = BTreeMap::new();
-        for _ in 0..len {
-            let key = Decodable::decode(d);
-            let val = Decodable::decode(d);
-            map.insert(key, val);
-        }
-        map
-    }
-}
-
-impl<S: Encoder, T> Encodable<S> for BTreeSet<T>
-where
-    T: Encodable<S> + PartialEq + Ord,
-{
-    fn encode(&self, s: &mut S) {
-        s.emit_usize(self.len());
-        for e in self.iter() {
-            e.encode(s);
-        }
-    }
-}
-
-impl<D: Decoder, T> Decodable<D> for BTreeSet<T>
-where
-    T: Decodable<D> + PartialEq + Ord,
-{
-    fn decode(d: &mut D) -> BTreeSet<T> {
-        let len = d.read_usize();
-        let mut set = BTreeSet::new();
-        for _ in 0..len {
-            set.insert(Decodable::decode(d));
-        }
-        set
-    }
-}
-
-impl<E: Encoder, K, V, S> Encodable<E> for HashMap<K, V, S>
-where
-    K: Encodable<E> + Eq,
-    V: Encodable<E>,
-    S: BuildHasher,
-{
-    fn encode(&self, e: &mut E) {
-        e.emit_usize(self.len());
-        for (key, val) in self.iter() {
-            key.encode(e);
-            val.encode(e);
-        }
-    }
-}
-
-impl<D: Decoder, K, V, S> Decodable<D> for HashMap<K, V, S>
-where
-    K: Decodable<D> + Hash + Eq,
-    V: Decodable<D>,
-    S: BuildHasher + Default,
-{
-    fn decode(d: &mut D) -> HashMap<K, V, S> {
-        let len = d.read_usize();
-        let state = Default::default();
-        let mut map = HashMap::with_capacity_and_hasher(len, state);
-        for _ in 0..len {
-            let key = Decodable::decode(d);
-            let val = Decodable::decode(d);
-            map.insert(key, val);
-        }
-        map
-    }
-}
-
-impl<E: Encoder, T, S> Encodable<E> for HashSet<T, S>
-where
-    T: Encodable<E> + Eq,
-    S: BuildHasher,
-{
-    fn encode(&self, s: &mut E) {
-        s.emit_usize(self.len());
-        for e in self.iter() {
-            e.encode(s);
-        }
-    }
-}
-
-impl<D: Decoder, T, S> Decodable<D> for HashSet<T, S>
-where
-    T: Decodable<D> + Hash + Eq,
-    S: BuildHasher + Default,
-{
-    fn decode(d: &mut D) -> HashSet<T, S> {
-        let len = d.read_usize();
-        let state = Default::default();
-        let mut set = HashSet::with_capacity_and_hasher(len, state);
-        for _ in 0..len {
-            set.insert(Decodable::decode(d));
-        }
-        set
-    }
-}
-
-impl<E: Encoder, K, V, S> Encodable<E> for indexmap::IndexMap<K, V, S>
-where
-    K: Encodable<E> + Hash + Eq,
-    V: Encodable<E>,
-    S: BuildHasher,
-{
-    fn encode(&self, e: &mut E) {
-        e.emit_usize(self.len());
-        for (key, val) in self.iter() {
-            key.encode(e);
-            val.encode(e);
-        }
-    }
-}
-
-impl<D: Decoder, K, V, S> Decodable<D> for indexmap::IndexMap<K, V, S>
-where
-    K: Decodable<D> + Hash + Eq,
-    V: Decodable<D>,
-    S: BuildHasher + Default,
-{
-    fn decode(d: &mut D) -> indexmap::IndexMap<K, V, S> {
-        let len = d.read_usize();
-        let state = Default::default();
-        let mut map = indexmap::IndexMap::with_capacity_and_hasher(len, state);
-        for _ in 0..len {
-            let key = Decodable::decode(d);
-            let val = Decodable::decode(d);
-            map.insert(key, val);
-        }
-        map
-    }
-}
-
-impl<E: Encoder, T, S> Encodable<E> for indexmap::IndexSet<T, S>
-where
-    T: Encodable<E> + Hash + Eq,
-    S: BuildHasher,
-{
-    fn encode(&self, s: &mut E) {
-        s.emit_usize(self.len());
-        for e in self.iter() {
-            e.encode(s);
-        }
-    }
-}
-
-impl<D: Decoder, T, S> Decodable<D> for indexmap::IndexSet<T, S>
-where
-    T: Decodable<D> + Hash + Eq,
-    S: BuildHasher + Default,
-{
-    fn decode(d: &mut D) -> indexmap::IndexSet<T, S> {
-        let len = d.read_usize();
-        let state = Default::default();
-        let mut set = indexmap::IndexSet::with_capacity_and_hasher(len, state);
-        for _ in 0..len {
-            set.insert(Decodable::decode(d));
-        }
-        set
-    }
-}
-
-impl<E: Encoder, T: Encodable<E>> Encodable<E> for Rc<[T]> {
-    fn encode(&self, s: &mut E) {
-        let slice: &[T] = self;
-        slice.encode(s);
-    }
-}
-
-impl<D: Decoder, T: Decodable<D>> Decodable<D> for Rc<[T]> {
-    fn decode(d: &mut D) -> Rc<[T]> {
-        let vec: Vec<T> = Decodable::decode(d);
-        vec.into()
-    }
-}
-
-impl<E: Encoder, T: Encodable<E>> Encodable<E> for Arc<[T]> {
-    fn encode(&self, s: &mut E) {
-        let slice: &[T] = self;
-        slice.encode(s);
-    }
-}
-
-impl<D: Decoder, T: Decodable<D>> Decodable<D> for Arc<[T]> {
-    fn decode(d: &mut D) -> Arc<[T]> {
-        let vec: Vec<T> = Decodable::decode(d);
-        vec.into()
-    }
-}
diff --git a/compiler/rustc_serialize/src/lib.rs b/compiler/rustc_serialize/src/lib.rs
index bd306eed85a..5360aa9ea6a 100644
--- a/compiler/rustc_serialize/src/lib.rs
+++ b/compiler/rustc_serialize/src/lib.rs
@@ -21,7 +21,6 @@
 
 pub use self::serialize::{Decodable, Decoder, Encodable, Encoder};
 
-mod collection_impls;
 mod serialize;
 
 pub mod leb128;
diff --git a/compiler/rustc_serialize/src/serialize.rs b/compiler/rustc_serialize/src/serialize.rs
index 06166cabc18..704de14dd46 100644
--- a/compiler/rustc_serialize/src/serialize.rs
+++ b/compiler/rustc_serialize/src/serialize.rs
@@ -1,12 +1,16 @@
 //! Support code for encoding and decoding types.
 
+use smallvec::{Array, SmallVec};
 use std::alloc::Allocator;
 use std::borrow::Cow;
 use std::cell::{Cell, RefCell};
+use std::collections::{BTreeMap, BTreeSet, HashMap, HashSet, VecDeque};
+use std::hash::{BuildHasher, Hash};
 use std::marker::PhantomData;
 use std::path;
 use std::rc::Rc;
 use std::sync::Arc;
+use thin_vec::ThinVec;
 
 /// A byte that [cannot occur in UTF8 sequences][utf8]. Used to mark the end of a string.
 /// This way we can skip validation and still be relatively sure that deserialization
@@ -509,3 +513,257 @@ fn decode(d: &mut D) -> Box<T, A> {
         Box::new_in(Decodable::decode(d), allocator)
     }
 }
+
+impl<S: Encoder, A: Array<Item: Encodable<S>>> Encodable<S> for SmallVec<A> {
+    fn encode(&self, s: &mut S) {
+        let slice: &[A::Item] = self;
+        slice.encode(s);
+    }
+}
+
+impl<D: Decoder, A: Array<Item: Decodable<D>>> Decodable<D> for SmallVec<A> {
+    fn decode(d: &mut D) -> SmallVec<A> {
+        let len = d.read_usize();
+        (0..len).map(|_| Decodable::decode(d)).collect()
+    }
+}
+
+impl<S: Encoder, T: Encodable<S>> Encodable<S> for ThinVec<T> {
+    fn encode(&self, s: &mut S) {
+        self.as_slice().encode(s);
+    }
+}
+
+impl<D: Decoder, T: Decodable<D>> Decodable<D> for ThinVec<T> {
+    fn decode(d: &mut D) -> ThinVec<T> {
+        let len = d.read_usize();
+        (0..len).map(|_| Decodable::decode(d)).collect()
+    }
+}
+
+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() {
+            e.encode(s);
+        }
+    }
+}
+
+impl<D: Decoder, T: Decodable<D>> Decodable<D> for VecDeque<T> {
+    fn decode(d: &mut D) -> VecDeque<T> {
+        let len = d.read_usize();
+        (0..len).map(|_| Decodable::decode(d)).collect()
+    }
+}
+
+impl<S: Encoder, K, V> Encodable<S> for BTreeMap<K, V>
+where
+    K: Encodable<S> + PartialEq + Ord,
+    V: Encodable<S>,
+{
+    fn encode(&self, e: &mut S) {
+        e.emit_usize(self.len());
+        for (key, val) in self.iter() {
+            key.encode(e);
+            val.encode(e);
+        }
+    }
+}
+
+impl<D: Decoder, K, V> Decodable<D> for BTreeMap<K, V>
+where
+    K: Decodable<D> + PartialEq + Ord,
+    V: Decodable<D>,
+{
+    fn decode(d: &mut D) -> BTreeMap<K, V> {
+        let len = d.read_usize();
+        let mut map = BTreeMap::new();
+        for _ in 0..len {
+            let key = Decodable::decode(d);
+            let val = Decodable::decode(d);
+            map.insert(key, val);
+        }
+        map
+    }
+}
+
+impl<S: Encoder, T> Encodable<S> for BTreeSet<T>
+where
+    T: Encodable<S> + PartialEq + Ord,
+{
+    fn encode(&self, s: &mut S) {
+        s.emit_usize(self.len());
+        for e in self.iter() {
+            e.encode(s);
+        }
+    }
+}
+
+impl<D: Decoder, T> Decodable<D> for BTreeSet<T>
+where
+    T: Decodable<D> + PartialEq + Ord,
+{
+    fn decode(d: &mut D) -> BTreeSet<T> {
+        let len = d.read_usize();
+        let mut set = BTreeSet::new();
+        for _ in 0..len {
+            set.insert(Decodable::decode(d));
+        }
+        set
+    }
+}
+
+impl<E: Encoder, K, V, S> Encodable<E> for HashMap<K, V, S>
+where
+    K: Encodable<E> + Eq,
+    V: Encodable<E>,
+    S: BuildHasher,
+{
+    fn encode(&self, e: &mut E) {
+        e.emit_usize(self.len());
+        for (key, val) in self.iter() {
+            key.encode(e);
+            val.encode(e);
+        }
+    }
+}
+
+impl<D: Decoder, K, V, S> Decodable<D> for HashMap<K, V, S>
+where
+    K: Decodable<D> + Hash + Eq,
+    V: Decodable<D>,
+    S: BuildHasher + Default,
+{
+    fn decode(d: &mut D) -> HashMap<K, V, S> {
+        let len = d.read_usize();
+        let state = Default::default();
+        let mut map = HashMap::with_capacity_and_hasher(len, state);
+        for _ in 0..len {
+            let key = Decodable::decode(d);
+            let val = Decodable::decode(d);
+            map.insert(key, val);
+        }
+        map
+    }
+}
+
+impl<E: Encoder, T, S> Encodable<E> for HashSet<T, S>
+where
+    T: Encodable<E> + Eq,
+    S: BuildHasher,
+{
+    fn encode(&self, s: &mut E) {
+        s.emit_usize(self.len());
+        for e in self.iter() {
+            e.encode(s);
+        }
+    }
+}
+
+impl<D: Decoder, T, S> Decodable<D> for HashSet<T, S>
+where
+    T: Decodable<D> + Hash + Eq,
+    S: BuildHasher + Default,
+{
+    fn decode(d: &mut D) -> HashSet<T, S> {
+        let len = d.read_usize();
+        let state = Default::default();
+        let mut set = HashSet::with_capacity_and_hasher(len, state);
+        for _ in 0..len {
+            set.insert(Decodable::decode(d));
+        }
+        set
+    }
+}
+
+impl<E: Encoder, K, V, S> Encodable<E> for indexmap::IndexMap<K, V, S>
+where
+    K: Encodable<E> + Hash + Eq,
+    V: Encodable<E>,
+    S: BuildHasher,
+{
+    fn encode(&self, e: &mut E) {
+        e.emit_usize(self.len());
+        for (key, val) in self.iter() {
+            key.encode(e);
+            val.encode(e);
+        }
+    }
+}
+
+impl<D: Decoder, K, V, S> Decodable<D> for indexmap::IndexMap<K, V, S>
+where
+    K: Decodable<D> + Hash + Eq,
+    V: Decodable<D>,
+    S: BuildHasher + Default,
+{
+    fn decode(d: &mut D) -> indexmap::IndexMap<K, V, S> {
+        let len = d.read_usize();
+        let state = Default::default();
+        let mut map = indexmap::IndexMap::with_capacity_and_hasher(len, state);
+        for _ in 0..len {
+            let key = Decodable::decode(d);
+            let val = Decodable::decode(d);
+            map.insert(key, val);
+        }
+        map
+    }
+}
+
+impl<E: Encoder, T, S> Encodable<E> for indexmap::IndexSet<T, S>
+where
+    T: Encodable<E> + Hash + Eq,
+    S: BuildHasher,
+{
+    fn encode(&self, s: &mut E) {
+        s.emit_usize(self.len());
+        for e in self.iter() {
+            e.encode(s);
+        }
+    }
+}
+
+impl<D: Decoder, T, S> Decodable<D> for indexmap::IndexSet<T, S>
+where
+    T: Decodable<D> + Hash + Eq,
+    S: BuildHasher + Default,
+{
+    fn decode(d: &mut D) -> indexmap::IndexSet<T, S> {
+        let len = d.read_usize();
+        let state = Default::default();
+        let mut set = indexmap::IndexSet::with_capacity_and_hasher(len, state);
+        for _ in 0..len {
+            set.insert(Decodable::decode(d));
+        }
+        set
+    }
+}
+
+impl<E: Encoder, T: Encodable<E>> Encodable<E> for Rc<[T]> {
+    fn encode(&self, s: &mut E) {
+        let slice: &[T] = self;
+        slice.encode(s);
+    }
+}
+
+impl<D: Decoder, T: Decodable<D>> Decodable<D> for Rc<[T]> {
+    fn decode(d: &mut D) -> Rc<[T]> {
+        let vec: Vec<T> = Decodable::decode(d);
+        vec.into()
+    }
+}
+
+impl<E: Encoder, T: Encodable<E>> Encodable<E> for Arc<[T]> {
+    fn encode(&self, s: &mut E) {
+        let slice: &[T] = self;
+        slice.encode(s);
+    }
+}
+
+impl<D: Decoder, T: Decodable<D>> Decodable<D> for Arc<[T]> {
+    fn decode(d: &mut D) -> Arc<[T]> {
+        let vec: Vec<T> = Decodable::decode(d);
+        vec.into()
+    }
+}