diff --git a/src/libcore/container.rs b/src/libcore/container.rs
index 272a2efc035..0a79a0ae19d 100644
--- a/src/libcore/container.rs
+++ b/src/libcore/container.rs
@@ -65,4 +65,26 @@ pub trait Set<T>: Mutable {
     /// Remove a value from the set. Return true if the value was
     /// present in the set.
     fn remove(&mut self, value: &T) -> bool;
+
+    /// Return true if the set has no elements in common with `other`.
+    /// This is equivalent to checking for an empty intersection.
+    pure fn is_disjoint(&self, other: &self) -> bool;
+
+    /// Return true if the set is a subset of another
+    pure fn is_subset(&self, other: &self) -> bool;
+
+    /// Return true if the set is a superset of another
+    pure fn is_superset(&self, other: &self) -> bool;
+
+    /// Visit the values representing the difference
+    pure fn difference(&self, other: &self, f: fn(&T) -> bool);
+
+    /// Visit the values representing the symmetric difference
+    pure fn symmetric_difference(&self, other: &self, f: fn(&T) -> bool);
+
+    /// Visit the values representing the intersection
+    pure fn intersection(&self, other: &self, f: fn(&T) -> bool);
+
+    /// Visit the values representing the union
+    pure fn union(&self, other: &self, f: fn(&T) -> bool);
 }
diff --git a/src/libcore/hashmap.rs b/src/libcore/hashmap.rs
index 4a3ee18440b..bef1069eef1 100644
--- a/src/libcore/hashmap.rs
+++ b/src/libcore/hashmap.rs
@@ -14,17 +14,17 @@
 #[forbid(deprecated_mode)];
 #[forbid(deprecated_pattern)];
 
+use container::{Container, Mutable, Map, Set};
 use cmp::Eq;
 use hash::Hash;
 use to_bytes::IterBytes;
 
 /// Open addressing with linear probing.
 pub mod linear {
+    use super::*;
     use iter::BaseIter;
-    use container::{Container, Mutable, Map, Set};
-    use cmp::Eq;
-    use cmp;
     use hash::Hash;
+    use iter;
     use kinds::Copy;
     use option::{None, Option, Some};
     use option;
@@ -453,6 +453,60 @@ pub mod linear {
         /// Remove a value from the set. Return true if the value was
         /// present in the set.
         fn remove(&mut self, value: &T) -> bool { self.map.remove(value) }
+
+        /// Return true if the set has no elements in common with `other`.
+        /// This is equivalent to checking for an empty intersection.
+        pure fn is_disjoint(&self, other: &LinearSet<T>) -> bool {
+            iter::all(self, |v| !other.contains(v))
+        }
+
+        /// Return true if the set is a subset of another
+        pure fn is_subset(&self, other: &LinearSet<T>) -> bool {
+            iter::all(self, |v| other.contains(v))
+        }
+
+        /// Return true if the set is a superset of another
+        pure fn is_superset(&self, other: &LinearSet<T>) -> bool {
+            other.is_subset(self)
+        }
+
+        /// Visit the values representing the difference
+        pure fn difference(&self, other: &LinearSet<T>, f: fn(&T) -> bool) {
+            for self.each |v| {
+                if !other.contains(v) {
+                    if !f(v) { return }
+                }
+            }
+        }
+
+        /// Visit the values representing the symmetric difference
+        pure fn symmetric_difference(&self, other: &LinearSet<T>,
+                                     f: fn(&T) -> bool) {
+            self.difference(other, f);
+            other.difference(self, f);
+        }
+
+        /// Visit the values representing the intersection
+        pure fn intersection(&self, other: &LinearSet<T>, f: fn(&T) -> bool) {
+            for self.each |v| {
+                if other.contains(v) {
+                    if !f(v) { return }
+                }
+            }
+        }
+
+        /// Visit the values representing the union
+        pure fn union(&self, other: &LinearSet<T>, f: fn(&T) -> bool) {
+            for self.each |v| {
+                if !f(v) { return }
+            }
+
+            for other.each |v| {
+                if !self.contains(v) {
+                    if !f(v) { return }
+                }
+            }
+        }
     }
 
     pub impl <T: Hash IterBytes Eq> LinearSet<T> {
@@ -462,7 +516,7 @@ pub mod linear {
 }
 
 #[test]
-pub mod test {
+mod test_map {
     use container::{Container, Mutable, Map, Set};
     use option::{None, Some};
     use hashmap::linear::LinearMap;
@@ -610,3 +664,168 @@ pub mod test {
         assert !m.is_empty();
     }
 }
+
+#[test]
+mod test_set {
+    use super::*;
+
+    #[test]
+    fn test_disjoint() {
+        let mut xs = linear::LinearSet::new();
+        let mut ys = linear::LinearSet::new();
+        assert xs.is_disjoint(&ys);
+        assert ys.is_disjoint(&xs);
+        assert xs.insert(5);
+        assert ys.insert(11);
+        assert xs.is_disjoint(&ys);
+        assert ys.is_disjoint(&xs);
+        assert xs.insert(7);
+        assert xs.insert(19);
+        assert xs.insert(4);
+        assert ys.insert(2);
+        assert ys.insert(-11);
+        assert xs.is_disjoint(&ys);
+        assert ys.is_disjoint(&xs);
+        assert ys.insert(7);
+        assert !xs.is_disjoint(&ys);
+        assert !ys.is_disjoint(&xs);
+    }
+
+    #[test]
+    fn test_subset_and_superset() {
+        let mut a = linear::LinearSet::new();
+        assert a.insert(0);
+        assert a.insert(5);
+        assert a.insert(11);
+        assert a.insert(7);
+
+        let mut b = linear::LinearSet::new();
+        assert b.insert(0);
+        assert b.insert(7);
+        assert b.insert(19);
+        assert b.insert(250);
+        assert b.insert(11);
+        assert b.insert(200);
+
+        assert !a.is_subset(&b);
+        assert !a.is_superset(&b);
+        assert !b.is_subset(&a);
+        assert !b.is_superset(&a);
+
+        assert b.insert(5);
+
+        assert a.is_subset(&b);
+        assert !a.is_superset(&b);
+        assert !b.is_subset(&a);
+        assert b.is_superset(&a);
+    }
+
+    #[test]
+    fn test_intersection() {
+        let mut a = linear::LinearSet::new();
+        let mut b = linear::LinearSet::new();
+
+        assert a.insert(11);
+        assert a.insert(1);
+        assert a.insert(3);
+        assert a.insert(77);
+        assert a.insert(103);
+        assert a.insert(5);
+        assert a.insert(-5);
+
+        assert b.insert(2);
+        assert b.insert(11);
+        assert b.insert(77);
+        assert b.insert(-9);
+        assert b.insert(-42);
+        assert b.insert(5);
+        assert b.insert(3);
+
+        let mut i = 0;
+        let expected = [3, 5, 11, 77];
+        for a.intersection(&b) |x| {
+            assert vec::contains(expected, x);
+            i += 1
+        }
+        assert i == expected.len();
+    }
+
+    #[test]
+    fn test_difference() {
+        let mut a = linear::LinearSet::new();
+        let mut b = linear::LinearSet::new();
+
+        assert a.insert(1);
+        assert a.insert(3);
+        assert a.insert(5);
+        assert a.insert(9);
+        assert a.insert(11);
+
+        assert b.insert(3);
+        assert b.insert(9);
+
+        let mut i = 0;
+        let expected = [1, 5, 11];
+        for a.difference(&b) |x| {
+            assert vec::contains(expected, x);
+            i += 1
+        }
+        assert i == expected.len();
+    }
+
+    #[test]
+    fn test_symmetric_difference() {
+        let mut a = linear::LinearSet::new();
+        let mut b = linear::LinearSet::new();
+
+        assert a.insert(1);
+        assert a.insert(3);
+        assert a.insert(5);
+        assert a.insert(9);
+        assert a.insert(11);
+
+        assert b.insert(-2);
+        assert b.insert(3);
+        assert b.insert(9);
+        assert b.insert(14);
+        assert b.insert(22);
+
+        let mut i = 0;
+        let expected = [-2, 1, 5, 11, 14, 22];
+        for a.symmetric_difference(&b) |x| {
+            assert vec::contains(expected, x);
+            i += 1
+        }
+        assert i == expected.len();
+    }
+
+    #[test]
+    fn test_union() {
+        let mut a = linear::LinearSet::new();
+        let mut b = linear::LinearSet::new();
+
+        assert a.insert(1);
+        assert a.insert(3);
+        assert a.insert(5);
+        assert a.insert(9);
+        assert a.insert(11);
+        assert a.insert(16);
+        assert a.insert(19);
+        assert a.insert(24);
+
+        assert b.insert(-2);
+        assert b.insert(1);
+        assert b.insert(5);
+        assert b.insert(9);
+        assert b.insert(13);
+        assert b.insert(19);
+
+        let mut i = 0;
+        let expected = [-2, 1, 3, 5, 9, 11, 13, 16, 19, 24];
+        for a.union(&b) |x| {
+            assert vec::contains(expected, x);
+            i += 1
+        }
+        assert i == expected.len();
+    }
+}
diff --git a/src/libstd/treemap.rs b/src/libstd/treemap.rs
index 82090f8dd62..1105d65a4ed 100644
--- a/src/libstd/treemap.rs
+++ b/src/libstd/treemap.rs
@@ -29,10 +29,10 @@ use core::prelude::*;
 // range search - O(log n) retrieval of an iterator from some key
 
 // (possibly) implement the overloads Python does for sets:
-//   * union: |
 //   * intersection: &
 //   * difference: -
 //   * symmetric difference: ^
+//   * union: |
 // These would be convenient since the methods work like `each`
 
 pub struct TreeMap<K, V> {
@@ -49,10 +49,9 @@ impl <K: Eq Ord, V: Eq> TreeMap<K, V>: Eq {
             let mut y = other.iter();
             for self.len().times {
                 unsafe { // unsafe as a purity workaround
-                    // ICE: x.next() != y.next()
-
                     x = x.next();
                     y = y.next();
+                    // FIXME: #4492 (ICE), x.get() == y.get()
                     let (x1, x2) = x.get().unwrap();
                     let (y1, y2) = y.get().unwrap();
 
@@ -292,22 +291,6 @@ impl <T: Ord> TreeSet<T>: Set<T> {
     /// Remove a value from the set. Return true if the value was
     /// present in the set.
     fn remove(&mut self, value: &T) -> bool { self.map.remove(value) }
-}
-
-impl <T: Ord> TreeSet<T> {
-    /// Create an empty TreeSet
-    static pure fn new() -> TreeSet<T> { TreeSet{map: TreeMap::new()} }
-
-    /// Visit all values in reverse order
-    pure fn each_reverse(&self, f: fn(&T) -> bool) {
-        self.map.each_key_reverse(f)
-    }
-
-    /// Get a lazy iterator over the values in the set.
-    /// Requires that it be frozen (immutable).
-    pure fn iter(&self) -> TreeSetIterator/&self<T> {
-        TreeSetIterator{iter: self.map.iter()}
-    }
 
     /// Return true if the set has no elements in common with `other`.
     /// This is equivalent to checking for an empty intersection.
@@ -336,12 +319,12 @@ impl <T: Ord> TreeSet<T> {
         true
     }
 
-    /// Check of the set is a subset of another
+    /// Return true if the set is a subset of another
     pure fn is_subset(&self, other: &TreeSet<T>) -> bool {
         other.is_superset(self)
     }
 
-    /// Check of the set is a superset of another
+    /// Return true if the set is a superset of another
     pure fn is_superset(&self, other: &TreeSet<T>) -> bool {
         let mut x = self.iter();
         let mut y = other.iter();
@@ -517,6 +500,22 @@ impl <T: Ord> TreeSet<T> {
     }
 }
 
+impl <T: Ord> TreeSet<T> {
+    /// Create an empty TreeSet
+    static pure fn new() -> TreeSet<T> { TreeSet{map: TreeMap::new()} }
+
+    /// Visit all values in reverse order
+    pure fn each_reverse(&self, f: fn(&T) -> bool) {
+        self.map.each_key_reverse(f)
+    }
+
+    /// Get a lazy iterator over the values in the set.
+    /// Requires that it be frozen (immutable).
+    pure fn iter(&self) -> TreeSetIterator/&self<T> {
+        TreeSetIterator{iter: self.map.iter()}
+    }
+}
+
 /// Lazy forward iterator over a set
 pub struct TreeSetIterator<T> {
     priv iter: TreeMapIterator<T, ()>
@@ -652,14 +651,12 @@ fn remove<K: Ord, V>(node: &mut Option<~TreeNode<K, V>>, key: &K) -> bool {
                     let mut left = save.left.swap_unwrap();
                     if left.right.is_some() {
                         heir_swap(save, &mut left.right);
-                        save.left = Some(left);
-                        remove(&mut save.left, key);
                     } else {
                         save.key <-> left.key;
                         save.value <-> left.value;
-                        save.left = Some(left);
-                        remove(&mut save.left, key);
                     }
+                    save.left = Some(left);
+                    remove(&mut save.left, key);
                 } else {
                     save = save.left.swap_unwrap();
                 }
@@ -969,9 +966,7 @@ mod test_treemap {
         let m = m;
         let mut iter = m.iter();
 
-        // ICE:
-        //assert iter.next() == Some((&x1, &y1));
-        //assert iter.next().eq(&Some((&x1, &y1)));
+        // FIXME: #4492 (ICE): iter.next() == Some((&x1, &y1))
 
         iter = iter.next();
         assert iter.get().unwrap() == (&x1, &y1);
@@ -984,10 +979,6 @@ mod test_treemap {
         iter = iter.next();
         assert iter.get().unwrap() == (&x5, &y5);
 
-        // ICE:
-        //assert iter.next() == None;
-        //assert iter.next().eq(&None);
-
         iter = iter.next();
         assert iter.get().is_none();
     }