diff --git a/src/libcore/container.rs b/src/libcore/container.rs
index 619622ceb95..062416838cc 100644
--- a/src/libcore/container.rs
+++ b/src/libcore/container.rs
@@ -10,7 +10,46 @@
 
 //! Container traits
 
-pub trait Set<T> {
+#[forbid(deprecated_mode)];
+#[forbid(deprecated_pattern)];
+
+pub trait Container {
+    /// Return the number of elements in the container
+    pure fn len(&self) -> uint;
+
+    /// Return true if the container contains no elements
+    pure fn is_empty(&self) -> bool;
+}
+
+pub trait Mutable: Container {
+    /// Clear the container, removing all values.
+    fn clear(&mut self);
+}
+
+pub trait Map<K, V>: Mutable {
+    /// Return true if the map contains a value for the specified key
+    pure fn contains_key(&self, key: &K) -> bool;
+
+    /// Visit all key-value pairs
+    pure fn each(&self, f: fn(&K, &V) -> bool);
+
+    /// Visit all keys
+    pure fn each_key(&self, f: fn(&K) -> bool);
+
+    /// Visit all values
+    pure fn each_value(&self, f: fn(&V) -> bool);
+
+    /// Insert a key-value pair into the map. An existing value for a
+    /// key is replaced by the new value. Return true if the key did
+    /// not already exist in the map.
+    fn insert(&mut self, key: K, value: V) -> bool;
+
+    /// Remove a key-value pair from the map. Return true if the key
+    /// was present in the map, otherwise false.
+    fn remove(&mut self, key: &K) -> bool;
+}
+
+pub trait Set<T>: Mutable {
     /// Return true if the set contains a value
     pure fn contains(&self, value: &T) -> bool;
 
diff --git a/src/libcore/send_map.rs b/src/libcore/send_map.rs
index 1e526c5d08f..dc4e24c4f8a 100644
--- a/src/libcore/send_map.rs
+++ b/src/libcore/send_map.rs
@@ -23,31 +23,10 @@ use hash::Hash;
 use prelude::*;
 use to_bytes::IterBytes;
 
-pub trait SendMap<K:Eq Hash, V: Copy> {
-    // FIXME(#3148)  ^^^^ once find_ref() works, we can drop V:copy
-
-    fn insert(&mut self, k: K, +v: V) -> bool;
-    fn remove(&mut self, k: &K) -> bool;
-    fn pop(&mut self, k: &K) -> Option<V>;
-    fn swap(&mut self, k: K, +v: V) -> Option<V>;
-    fn consume(&mut self, f: fn(K, V));
-    fn clear(&mut self);
-    pure fn len(&const self) -> uint;
-    pure fn is_empty(&const self) -> bool;
-    pure fn contains_key(&const self, k: &K) -> bool;
-    pure fn each(&self, blk: fn(k: &K, v: &V) -> bool);
-    pure fn each_key_ref(&self, blk: fn(k: &K) -> bool);
-    pure fn each_value_ref(&self, blk: fn(v: &V) -> bool);
-    pure fn find(&const self, k: &K) -> Option<V>;
-    pure fn get(&const self, k: &K) -> V;
-    pure fn find_ref(&self, k: &K) -> Option<&self/V>;
-    pure fn get_ref(&self, k: &K) -> &self/V;
-}
-
 /// Open addressing with linear probing.
 pub mod linear {
     use iter::BaseIter;
-    use container::Set;
+    use container::{Container, Mutable, Map, Set};
     use cmp::Eq;
     use cmp;
     use hash::Hash;
@@ -279,7 +258,48 @@ pub mod linear {
         }
     }
 
-    impl<K:Hash IterBytes Eq,V> LinearMap<K,V> {
+    impl <K: Hash IterBytes Eq, V> LinearMap<K, V>: Container {
+        pure fn len(&self) -> uint { self.size }
+        pure fn is_empty(&self) -> bool { self.len() == 0 }
+    }
+
+    impl <K: Hash IterBytes Eq, V> LinearMap<K, V>: Mutable {
+        fn clear(&mut self) {
+            for uint::range(0, self.buckets.len()) |idx| {
+                self.buckets[idx] = None;
+            }
+            self.size = 0;
+        }
+    }
+
+    impl <K: Hash IterBytes Eq, V> LinearMap<K, V>: Map<K, V> {
+        pure fn contains_key(&self, k: &K) -> bool {
+            match self.bucket_for_key(self.buckets, k) {
+                FoundEntry(_) => {true}
+                TableFull | FoundHole(_) => {false}
+            }
+        }
+
+        pure fn each(&self, blk: fn(k: &K, v: &V) -> bool) {
+            for vec::each(self.buckets) |slot| {
+                let mut broke = false;
+                do slot.iter |bucket| {
+                    if !blk(&bucket.key, &bucket.value) {
+                        broke = true; // FIXME(#3064) just write "break;"
+                    }
+                }
+                if broke { break; }
+            }
+        }
+
+        pure fn each_key(&self, blk: fn(k: &K) -> bool) {
+            self.each(|k, _v| blk(k))
+        }
+
+        pure fn each_value(&self, blk: fn(v: &V) -> bool) {
+            self.each(|_k, v| blk(v))
+        }
+
         fn insert(&mut self, k: K, v: V) -> bool {
             if self.size >= self.resize_at {
                 // n.b.: We could also do this after searching, so
@@ -301,7 +321,9 @@ pub mod linear {
                 None => false,
             }
         }
+    }
 
+    impl<K:Hash IterBytes Eq,V> LinearMap<K,V> {
         fn pop(&mut self, k: &K) -> Option<V> {
             let hash = k.hash_keyed(self.k0, self.k1) as uint;
             self.pop_internal(hash, k)
@@ -347,29 +369,6 @@ pub mod linear {
             }
         }
 
-        fn clear(&mut self) {
-            for uint::range(0, self.buckets.len()) |idx| {
-                self.buckets[idx] = None;
-            }
-            self.size = 0;
-        }
-
-        pure fn len(&const self) -> uint {
-            self.size
-        }
-
-        pure fn is_empty(&const self) -> bool {
-            self.len() == 0
-        }
-
-        pure fn contains_key(&const self,
-                        k: &K) -> bool {
-            match self.bucket_for_key(self.buckets, k) {
-                FoundEntry(_) => {true}
-                TableFull | FoundHole(_) => {false}
-            }
-        }
-
         pure fn find_ref(&self, k: &K) -> Option<&self/V> {
             match self.bucket_for_key(self.buckets, k) {
                 FoundEntry(idx) => {
@@ -396,26 +395,6 @@ pub mod linear {
                 None => fail fmt!("No entry found for key: %?", k),
             }
         }
-
-        pure fn each(&self, blk: fn(k: &K, v: &V) -> bool) {
-            for vec::each(self.buckets) |slot| {
-                let mut broke = false;
-                do slot.iter |bucket| {
-                    if !blk(&bucket.key, &bucket.value) {
-                        broke = true; // FIXME(#3064) just write "break;"
-                    }
-                }
-                if broke { break; }
-            }
-        }
-
-        pure fn each_key(&self, blk: fn(k: &K) -> bool) {
-            self.each(|k, _v| blk(k))
-        }
-
-        pure fn each_value(&self, blk: fn(v: &V) -> bool) {
-            self.each(|_k, v| blk(v))
-        }
     }
 
     impl<K:Hash IterBytes Eq, V: Copy> LinearMap<K,V> {
@@ -482,6 +461,15 @@ pub mod linear {
         }
     }
 
+    impl <T: Hash IterBytes Eq> LinearSet<T>: Container {
+        pure fn len(&self) -> uint { self.map.len() }
+        pure fn is_empty(&self) -> bool { self.map.is_empty() }
+    }
+
+    impl <T: Hash IterBytes Eq> LinearSet<T>: Mutable {
+        fn clear(&mut self) { self.map.clear() }
+    }
+
     impl <T: Hash IterBytes Eq> LinearSet<T>: Set<T> {
         /// Return true if the set contains a value
         pure fn contains(&self, value: &T) -> bool {
@@ -500,12 +488,6 @@ pub mod linear {
     impl <T: Hash IterBytes Eq> LinearSet<T> {
         /// Create an empty LinearSet
         static fn new() -> LinearSet<T> { LinearSet{map: LinearMap()} }
-
-        /// Return the number of elements in the set
-        pure fn len(&self) -> uint { self.map.len() }
-
-        /// Return true if the set contains no elements
-        pure fn is_empty(&self) -> bool { self.map.is_empty() }
     }
 }
 
diff --git a/src/libstd/priority_queue.rs b/src/libstd/priority_queue.rs
index b9c040de42a..ee78fafb60b 100644
--- a/src/libstd/priority_queue.rs
+++ b/src/libstd/priority_queue.rs
@@ -10,6 +10,7 @@
 
 //! A priority queue implemented with a binary heap
 
+use core::container::{Container, Mutable};
 use core::cmp::Ord;
 use core::prelude::*;
 use core::ptr::addr_of;
@@ -24,6 +25,19 @@ pub struct PriorityQueue <T: Ord>{
     priv data: ~[T],
 }
 
+impl <T: Ord> PriorityQueue<T>: Container {
+    /// Returns the length of the queue
+    pure fn len(&self) -> uint { self.data.len() }
+
+    /// Returns true if a queue contains no elements
+    pure fn is_empty(&self) -> bool { self.data.is_empty() }
+}
+
+impl <T: Ord> PriorityQueue<T>: Mutable {
+    /// Drop all items from the queue
+    fn clear(&mut self) { self.data.truncate(0) }
+}
+
 impl <T: Ord> PriorityQueue<T> {
     /// Returns the greatest item in the queue - fails if empty
     pure fn top(&self) -> &self/T { &self.data[0] }
@@ -33,12 +47,6 @@ impl <T: Ord> PriorityQueue<T> {
         if self.is_empty() { None } else { Some(self.top()) }
     }
 
-    /// Returns the length of the queue
-    pure fn len(&self) -> uint { self.data.len() }
-
-    /// Returns true if a queue contains no elements
-    pure fn is_empty(&self) -> bool { self.data.is_empty() }
-
     /// Returns true if a queue contains some elements
     pure fn is_not_empty(&self) -> bool { self.data.is_not_empty() }
 
@@ -51,9 +59,6 @@ impl <T: Ord> PriorityQueue<T> {
         vec::reserve_at_least(&mut self.data, n)
     }
 
-    /// Drop all items from the queue
-    fn clear(&mut self) { self.data.truncate(0) }
-
     /// Pop the greatest item from the queue - fails if empty
     fn pop(&mut self) -> T {
         let mut item = self.data.pop();
diff --git a/src/libstd/treemap.rs b/src/libstd/treemap.rs
index 1b20b35bda1..0bb8738773c 100644
--- a/src/libstd/treemap.rs
+++ b/src/libstd/treemap.rs
@@ -14,7 +14,7 @@
 
 #[forbid(deprecated_mode)];
 
-use core::container::Set;
+use core::container::{Container, Mutable, Map, Set};
 use core::cmp::{Eq, Ord};
 use core::option::{Option, Some, None};
 use core::prelude::*;
@@ -64,23 +64,30 @@ impl <K: Eq Ord, V: Eq> TreeMap<K, V>: Eq {
             true
         }
     }
-    pure fn ne(&self, other: &TreeMap<K, V>) -> bool {
-        !self.eq(other)
-    }
+    pure fn ne(&self, other: &TreeMap<K, V>) -> bool { !self.eq(other) }
 }
 
-impl <K: Ord, V> TreeMap<K, V> {
-    /// Create an empty TreeMap
-    static pure fn new() -> TreeMap<K, V> { TreeMap{root: None, length: 0} }
-
+impl <K: Ord, V> TreeMap<K, V>: Container {
     /// Return the number of elements in the map
     pure fn len(&self) -> uint { self.length }
 
     /// Return true if the map contains no elements
     pure fn is_empty(&self) -> bool { self.root.is_none() }
+}
 
-    /// Return true if the map contains some elements
-    pure fn is_not_empty(&self) -> bool { self.root.is_some() }
+impl <K: Ord, V> TreeMap<K, V>: Mutable {
+    /// Clear the map, removing all key-value pairs.
+    fn clear(&mut self) {
+        self.root = None;
+        self.length = 0
+    }
+}
+
+impl <K: Ord, V> TreeMap<K, V>: Map<K, V> {
+    /// Return true if the map contains a value for the specified key
+    pure fn contains_key(&self, key: &K) -> bool {
+        self.find(key).is_some()
+    }
 
     /// Visit all key-value pairs in order
     pure fn each(&self, f: fn(&K, &V) -> bool) { each(&self.root, f) }
@@ -91,6 +98,31 @@ impl <K: Ord, V> TreeMap<K, V> {
     /// Visit all values in order
     pure fn each_value(&self, f: fn(&V) -> bool) { self.each(|_, v| f(v)) }
 
+    /// Insert a key-value pair into the map. An existing value for a
+    /// key is replaced by the new value. Return true if the key did
+    /// not already exist in the map.
+    fn insert(&mut self, key: K, value: V) -> bool {
+        let ret = insert(&mut self.root, key, value);
+        if ret { self.length += 1 }
+        ret
+    }
+
+    /// Remove a key-value pair from the map. Return true if the key
+    /// was present in the map, otherwise false.
+    fn remove(&mut self, key: &K) -> bool {
+        let ret = remove(&mut self.root, key);
+        if ret { self.length -= 1 }
+        ret
+    }
+}
+
+impl <K: Ord, V> TreeMap<K, V> {
+    /// Create an empty TreeMap
+    static pure fn new() -> TreeMap<K, V> { TreeMap{root: None, length: 0} }
+
+    /// Return true if the map contains some elements
+    pure fn is_not_empty(&self) -> bool { self.root.is_some() }
+
     /// Visit all key-value pairs in reverse order
     pure fn each_reverse(&self, f: fn(&K, &V) -> bool) {
         each_reverse(&self.root, f);
@@ -106,11 +138,6 @@ impl <K: Ord, V> TreeMap<K, V> {
         self.each_reverse(|_, v| f(v))
     }
 
-    /// Return true if the map contains a value for the specified key
-    pure fn contains_key(&self, key: &K) -> bool {
-        self.find(key).is_some()
-    }
-
     /// Return the value corresponding to the key in the map
     pure fn find(&self, key: &K) -> Option<&self/V> {
         let mut current: &self/Option<~TreeNode<K, V>> = &self.root;
@@ -131,23 +158,6 @@ impl <K: Ord, V> TreeMap<K, V> {
         }
     }
 
-    /// Insert a key-value pair into the map. An existing value for a
-    /// key is replaced by the new value. Return true if the key did
-    /// not already exist in the map.
-    fn insert(&mut self, key: K, value: V) -> bool {
-        let ret = insert(&mut self.root, key, value);
-        if ret { self.length += 1 }
-        ret
-    }
-
-    /// Remove a key-value pair from the map. Return true if the key
-    /// was present in the map, otherwise false.
-    fn remove(&mut self, key: &K) -> bool {
-        let ret = remove(&mut self.root, key);
-        if ret { self.length -= 1 }
-        ret
-    }
-
     /// Get a lazy iterator over the key-value pairs in the map.
     /// Requires that it be frozen (immutable).
     pure fn iter(&self) -> TreeMapIterator/&self<K, V> {
@@ -198,6 +208,19 @@ impl <T: Eq Ord> TreeSet<T>: Eq {
     pure fn ne(&self, other: &TreeSet<T>) -> bool { self.map != other.map }
 }
 
+impl <T: Ord> TreeSet<T>: Container {
+    /// Return the number of elements in the map
+    pure fn len(&self) -> uint { self.map.len() }
+
+    /// Return true if the map contains no elements
+    pure fn is_empty(&self) -> bool { self.map.is_empty() }
+}
+
+impl <T: Ord> TreeSet<T>: Mutable {
+    /// Clear the set, removing all values.
+    fn clear(&mut self) { self.map.clear() }
+}
+
 impl <T: Ord> TreeSet<T>: Set<T> {
     /// Return true if the set contains a value
     pure fn contains(&self, value: &T) -> bool {
@@ -217,12 +240,6 @@ impl <T: Ord> TreeSet<T> {
     /// Create an empty TreeSet
     static pure fn new() -> TreeSet<T> { TreeSet{map: TreeMap::new()} }
 
-    /// Return the number of elements in the set
-    pure fn len(&self) -> uint { self.map.len() }
-
-    /// Return true if the set contains no elements
-    pure fn is_empty(&self) -> bool { self.map.is_empty() }
-
     /// Return true if the set contains some elements
     pure fn is_not_empty(&self) -> bool { self.map.is_not_empty() }
 
@@ -626,6 +643,20 @@ mod test_treemap {
         assert m.find(&2).unwrap() == &11;
     }
 
+    #[test]
+    fn test_clear() {
+        let mut m = TreeMap::new();
+        m.clear();
+        assert m.insert(5, 11);
+        assert m.insert(12, -3);
+        assert m.insert(19, 2);
+        m.clear();
+        assert m.find(&5).is_none();
+        assert m.find(&12).is_none();
+        assert m.find(&19).is_none();
+        assert m.is_empty();
+    }
+
     #[test]
     fn u8_map() {
         let mut m = TreeMap::new();
@@ -846,6 +877,20 @@ mod test_treemap {
 mod test_set {
     use super::*;
 
+    #[test]
+    fn test_clear() {
+        let mut s = TreeSet::new();
+        s.clear();
+        assert s.insert(5);
+        assert s.insert(12);
+        assert s.insert(19);
+        s.clear();
+        assert !s.contains(&5);
+        assert !s.contains(&12);
+        assert !s.contains(&19);
+        assert s.is_empty();
+    }
+
     #[test]
     fn test_disjoint() {
         let mut xs = TreeSet::new();