diff --git a/src/libstd/bitv.rs b/src/libstd/bitv.rs
index 75b97f494bd6..c72f9ec2f98d 100644
--- a/src/libstd/bitv.rs
+++ b/src/libstd/bitv.rs
@@ -16,11 +16,7 @@ use core::vec;
 
 struct SmallBitv {
     /// only the lowest nbits of this value are used. the rest is undefined.
-    mut bits: u32
-}
-
-fn SmallBitv(bits: u32) -> SmallBitv {
-    SmallBitv {bits: bits}
+    bits: u32
 }
 
 /// a mask that has a 1 for each defined bit in a small_bitv, assuming n bits
@@ -30,9 +26,13 @@ fn small_mask(nbits: uint) -> u32 {
 }
 
 impl SmallBitv {
+    static fn new(bits: u32) -> SmallBitv {
+        SmallBitv {bits: bits}
+    }
 
     #[inline(always)]
-    fn bits_op(right_bits: u32, nbits: uint, f: fn(u32, u32) -> u32) -> bool {
+    fn bits_op(&mut self, right_bits: u32, nbits: uint,
+               f: fn(u32, u32) -> u32) -> bool {
         let mask = small_mask(nbits);
         let old_b: u32 = self.bits;
         let new_b = f(old_b, right_bits);
@@ -41,32 +41,32 @@ impl SmallBitv {
     }
 
     #[inline(always)]
-    fn union(s: &SmallBitv, nbits: uint) -> bool {
+    fn union(&mut self, s: &SmallBitv, nbits: uint) -> bool {
         self.bits_op(s.bits, nbits, |u1, u2| u1 | u2)
     }
 
     #[inline(always)]
-    fn intersect(s: &SmallBitv, nbits: uint) -> bool {
+    fn intersect(&mut self, s: &SmallBitv, nbits: uint) -> bool {
         self.bits_op(s.bits, nbits, |u1, u2| u1 & u2)
     }
 
     #[inline(always)]
-    fn become(s: &SmallBitv, nbits: uint) -> bool {
+    fn become(&mut self, s: &SmallBitv, nbits: uint) -> bool {
         self.bits_op(s.bits, nbits, |_u1, u2| u2)
     }
 
     #[inline(always)]
-    fn difference(s: &SmallBitv, nbits: uint) -> bool {
+    fn difference(&mut self, s: &SmallBitv, nbits: uint) -> bool {
         self.bits_op(s.bits, nbits, |u1, u2| u1 & !u2)
     }
 
     #[inline(always)]
-    pure fn get(i: uint) -> bool {
+    pure fn get(&self, i: uint) -> bool {
         (self.bits & (1 << i)) != 0
     }
 
     #[inline(always)]
-    fn set(i: uint, x: bool) {
+    fn set(&mut self, i: uint, x: bool) {
         if x {
             self.bits |= 1<<i;
         }
@@ -76,39 +76,34 @@ impl SmallBitv {
     }
 
     #[inline(always)]
-    fn equals(b: &SmallBitv, nbits: uint) -> bool {
+    fn equals(&self, b: &SmallBitv, nbits: uint) -> bool {
         let mask = small_mask(nbits);
         mask & self.bits == mask & b.bits
     }
 
     #[inline(always)]
-    fn clear() { self.bits = 0; }
+    fn clear(&mut self) { self.bits = 0; }
 
     #[inline(always)]
-    fn set_all() { self.bits = !0; }
+    fn set_all(&mut self) { self.bits = !0; }
 
     #[inline(always)]
-    fn is_true(nbits: uint) -> bool {
+    fn is_true(&self, nbits: uint) -> bool {
         small_mask(nbits) & !self.bits == 0
     }
 
     #[inline(always)]
-    fn is_false(nbits: uint) -> bool {
+    fn is_false(&self, nbits: uint) -> bool {
         small_mask(nbits) & self.bits == 0
     }
 
     #[inline(always)]
-    fn invert() { self.bits = !self.bits; }
+    fn invert(&mut self) { self.bits = !self.bits; }
 
 }
 
 struct BigBitv {
-    // only mut b/c of clone and lack of other constructor
-    mut storage: ~[uint]
-}
-
-fn BigBitv(storage: ~[uint]) -> BigBitv {
-    BigBitv {storage: storage}
+    storage: ~[uint]
 }
 
 /**
@@ -128,9 +123,13 @@ fn big_mask(nbits: uint, elem: uint) -> uint {
 }
 
 impl BigBitv {
+    static fn new(storage: ~[uint]) -> BigBitv {
+        BigBitv {storage: storage}
+    }
 
     #[inline(always)]
-    fn process(b: &BigBitv, nbits: uint, op: fn(uint, uint) -> uint) -> bool {
+    fn process(&mut self, b: &BigBitv, nbits: uint,
+               op: fn(uint, uint) -> uint) -> bool {
         let len = b.storage.len();
         assert (self.storage.len() == len);
         let mut changed = false;
@@ -151,7 +150,7 @@ impl BigBitv {
     }
 
     #[inline(always)]
-     fn each_storage(op: fn(v: &mut uint) -> bool) {
+    fn each_storage(&mut self, op: fn(v: &mut uint) -> bool) {
         for uint::range(0, self.storage.len()) |i| {
             let mut w = self.storage[i];
             let b = op(&mut w);
@@ -161,30 +160,30 @@ impl BigBitv {
      }
 
     #[inline(always)]
-    fn invert() { for self.each_storage() |w| { *w = !*w } }
+    fn invert(&mut self) { for self.each_storage |w| { *w = !*w } }
 
     #[inline(always)]
-    fn union(b: &BigBitv, nbits: uint) -> bool {
+    fn union(&mut self, b: &BigBitv, nbits: uint) -> bool {
         self.process(b, nbits, lor)
     }
 
     #[inline(always)]
-    fn intersect(b: &BigBitv, nbits: uint) -> bool {
+    fn intersect(&mut self, b: &BigBitv, nbits: uint) -> bool {
         self.process(b, nbits, land)
     }
 
     #[inline(always)]
-    fn become(b: &BigBitv, nbits: uint) -> bool {
+    fn become(&mut self, b: &BigBitv, nbits: uint) -> bool {
         self.process(b, nbits, right)
     }
 
     #[inline(always)]
-    fn difference(b: &BigBitv, nbits: uint) -> bool {
+    fn difference(&mut self, b: &BigBitv, nbits: uint) -> bool {
         self.process(b, nbits, difference)
     }
 
     #[inline(always)]
-    pure fn get(i: uint) -> bool {
+    pure fn get(&self, i: uint) -> bool {
         let w = i / uint_bits;
         let b = i % uint_bits;
         let x = 1 & self.storage[w] >> b;
@@ -192,16 +191,16 @@ impl BigBitv {
     }
 
     #[inline(always)]
-    fn set(i: uint, x: bool) {
+    fn set(&mut self, i: uint, x: bool) {
         let w = i / uint_bits;
         let b = i % uint_bits;
         let flag = 1 << b;
         self.storage[w] = if x { self.storage[w] | flag }
-                 else { self.storage[w] & !flag };
+                          else { self.storage[w] & !flag };
     }
 
     #[inline(always)]
-    fn equals(b: &BigBitv, nbits: uint) -> bool {
+    fn equals(&self, b: &BigBitv, nbits: uint) -> bool {
         let len = b.storage.len();
         for uint::iterate(0, len) |i| {
             let mask = big_mask(nbits, i);
@@ -223,33 +222,19 @@ pub struct Bitv {
     nbits: uint
 }
 
-pub fn Bitv (nbits: uint, init: bool) -> Bitv {
-    let rep = if nbits <= 32 {
-        Small(~SmallBitv(if init {!0} else {0}))
-    }
-    else {
-        let nelems = nbits/uint_bits +
-                     if nbits % uint_bits == 0 {0} else {1};
-        let elem = if init {!0} else {0};
-        let s = from_elem(nelems, elem);
-        Big(~BigBitv(s))
-    };
-    Bitv {rep: rep, nbits: nbits}
-}
-
 priv impl Bitv {
 
-    fn die() -> ! {
+    fn die(&self) -> ! {
         fail!(~"Tried to do operation on bit vectors with different sizes");
     }
 
     #[inline(always)]
-    fn do_op(op: Op, other: &Bitv) -> bool {
+    fn do_op(&mut self, op: Op, other: &Bitv) -> bool {
         if self.nbits != other.nbits {
             self.die();
         }
         match self.rep {
-          Small(ref s) => match other.rep {
+          Small(ref mut s) => match other.rep {
             Small(ref s1) => match op {
               Union      => s.union(*s1,      self.nbits),
               Intersect  => s.intersect(*s1,  self.nbits),
@@ -258,7 +243,7 @@ priv impl Bitv {
             },
             Big(_) => self.die()
           },
-          Big(ref s) => match other.rep {
+          Big(ref mut s) => match other.rep {
             Small(_) => self.die(),
             Big(ref s1) => match op {
               Union      => s.union(*s1,      self.nbits),
@@ -273,6 +258,19 @@ priv impl Bitv {
 }
 
 impl Bitv {
+    static fn new(nbits: uint, init: bool) -> Bitv {
+        let rep = if nbits <= 32 {
+            Small(~SmallBitv::new(if init {!0} else {0}))
+        }
+        else {
+            let nelems = nbits/uint_bits +
+                         if nbits % uint_bits == 0 {0} else {1};
+            let elem = if init {!0} else {0};
+            let s = from_elem(nelems, elem);
+            Big(~BigBitv::new(s))
+        };
+        Bitv {rep: rep, nbits: nbits}
+    }
 
     /**
      * Calculates the union of two bitvectors
@@ -281,7 +279,7 @@ impl Bitv {
      * the same length. Returns 'true' if `self` changed.
     */
     #[inline(always)]
-    fn union(v1: &Bitv) -> bool { self.do_op(Union, v1) }
+    fn union(&mut self, v1: &Bitv) -> bool { self.do_op(Union, v1) }
 
     /**
      * Calculates the intersection of two bitvectors
@@ -290,7 +288,7 @@ impl Bitv {
      * must be the same length. Returns 'true' if `self` changed.
     */
     #[inline(always)]
-    fn intersect(v1: &Bitv) -> bool { self.do_op(Intersect, v1) }
+    fn intersect(&mut self, v1: &Bitv) -> bool { self.do_op(Intersect, v1) }
 
     /**
      * Assigns the value of `v1` to `self`
@@ -299,11 +297,11 @@ impl Bitv {
      * changed
      */
     #[inline(always)]
-    fn assign(v: &Bitv) -> bool { self.do_op(Assign, v) }
+    fn assign(&mut self, v: &Bitv) -> bool { self.do_op(Assign, v) }
 
     /// Retrieve the value at index `i`
     #[inline(always)]
-    pure fn get(i: uint) -> bool {
+    pure fn get(&self, i: uint) -> bool {
        assert (i < self.nbits);
        match self.rep {
          Big(ref b)   => b.get(i),
@@ -317,11 +315,11 @@ impl Bitv {
      * `i` must be less than the length of the bitvector.
      */
     #[inline(always)]
-    fn set(i: uint, x: bool) {
+    fn set(&mut self, i: uint, x: bool) {
       assert (i < self.nbits);
       match self.rep {
-        Big(ref b)   => b.set(i, x),
-        Small(ref s) => s.set(i, x)
+        Big(ref mut b)   => b.set(i, x),
+        Small(ref mut s) => s.set(i, x)
       }
     }
 
@@ -332,7 +330,7 @@ impl Bitv {
      * bitvectors contain identical elements.
      */
     #[inline(always)]
-    fn equal(v1: &Bitv) -> bool {
+    fn equal(&self, v1: &Bitv) -> bool {
       if self.nbits != v1.nbits { return false; }
       match self.rep {
         Small(ref b) => match v1.rep {
@@ -348,27 +346,27 @@ impl Bitv {
 
     /// Set all bits to 0
     #[inline(always)]
-    fn clear() {
+    fn clear(&mut self) {
         match self.rep {
-          Small(ref b) => b.clear(),
-          Big(ref s) => for s.each_storage() |w| { *w = 0u }
+          Small(ref mut b) => b.clear(),
+          Big(ref mut s) => for s.each_storage() |w| { *w = 0u }
         }
     }
 
     /// Set all bits to 1
     #[inline(always)]
-    fn set_all() {
+    fn set_all(&mut self) {
       match self.rep {
-        Small(ref b) => b.set_all(),
-        Big(ref s) => for s.each_storage() |w| { *w = !0u } }
+        Small(ref mut b) => b.set_all(),
+        Big(ref mut s) => for s.each_storage() |w| { *w = !0u } }
     }
 
     /// Invert all bits
     #[inline(always)]
-    fn invert() {
+    fn invert(&mut self) {
       match self.rep {
-        Small(ref b) => b.invert(),
-        Big(ref s) => for s.each_storage() |w| { *w = !*w } }
+        Small(ref mut b) => b.invert(),
+        Big(ref mut s) => for s.each_storage() |w| { *w = !*w } }
     }
 
     /**
@@ -381,11 +379,11 @@ impl Bitv {
      * Returns `true` if `v0` was changed.
      */
     #[inline(always)]
-    fn difference(v: &Bitv) -> bool { self.do_op(Difference, v) }
+    fn difference(&mut self, v: &Bitv) -> bool { self.do_op(Difference, v) }
 
     /// Returns true if all bits are 1
     #[inline(always)]
-    fn is_true() -> bool {
+    fn is_true(&self) -> bool {
       match self.rep {
         Small(ref b) => b.is_true(self.nbits),
         _ => {
@@ -396,7 +394,7 @@ impl Bitv {
     }
 
     #[inline(always)]
-    fn each(f: fn(bool) -> bool) {
+    fn each(&self, f: fn(bool) -> bool) {
         let mut i = 0;
         while i < self.nbits {
             if !f(self.get(i)) { break; }
@@ -405,7 +403,7 @@ impl Bitv {
     }
 
     /// Returns true if all bits are 0
-    fn is_false() -> bool {
+    fn is_false(&self) -> bool {
       match self.rep {
         Small(ref b) => b.is_false(self.nbits),
         Big(_) => {
@@ -415,7 +413,7 @@ impl Bitv {
       }
     }
 
-    fn init_to_vec(i: uint) -> uint {
+    fn init_to_vec(&self, i: uint) -> uint {
       return if self.get(i) { 1 } else { 0 };
     }
 
@@ -424,7 +422,7 @@ impl Bitv {
      *
      * Each uint in the resulting vector has either value 0u or 1u.
      */
-    fn to_vec() -> ~[uint] {
+    fn to_vec(&self) -> ~[uint] {
         vec::from_fn(self.nbits, |x| self.init_to_vec(x))
     }
 
@@ -434,7 +432,7 @@ impl Bitv {
      * size of the bitv is not a multiple of 8 then trailing bits
      * will be filled-in with false/0
      */
-    fn to_bytes() -> ~[u8] {
+    fn to_bytes(&self) -> ~[u8] {
 
         fn bit (bitv: &Bitv, byte: uint, bit: uint) -> u8 {
             let offset = byte * 8 + bit;
@@ -448,21 +446,21 @@ impl Bitv {
         let len = self.nbits/8 +
                   if self.nbits % 8 == 0 { 0 } else { 1 };
         vec::from_fn(len, |i|
-            bit(&self, i, 0) |
-            bit(&self, i, 1) |
-            bit(&self, i, 2) |
-            bit(&self, i, 3) |
-            bit(&self, i, 4) |
-            bit(&self, i, 5) |
-            bit(&self, i, 6) |
-            bit(&self, i, 7)
+            bit(self, i, 0) |
+            bit(self, i, 1) |
+            bit(self, i, 2) |
+            bit(self, i, 3) |
+            bit(self, i, 4) |
+            bit(self, i, 5) |
+            bit(self, i, 6) |
+            bit(self, i, 7)
         )
     }
 
     /**
      * Transform self into a [bool] by turning each bit into a bool
      */
-    fn to_bools() -> ~[bool] {
+    fn to_bools(&self) -> ~[bool] {
         vec::from_fn(self.nbits, |i| self[i])
     }
 
@@ -485,7 +483,7 @@ impl Bitv {
      * The uint vector is expected to only contain the values 0u and 1u. Both
      * the bitvector and vector must have the same length
      */
-    fn eq_vec(v: ~[uint]) -> bool {
+    fn eq_vec(&self, v: ~[uint]) -> bool {
         assert self.nbits == v.len();
         let mut i = 0;
         while i < self.nbits {
@@ -497,7 +495,7 @@ impl Bitv {
         true
     }
 
-    fn ones(f: fn(uint) -> bool) {
+    fn ones(&self, f: fn(uint) -> bool) {
         for uint::range(0, self.nbits) |i| {
             if self.get(i) {
                 if !f(i) { break }
@@ -551,7 +549,7 @@ pub fn from_bools(bools: &[bool]) -> Bitv {
  * index is f(index).
  */
 pub fn from_fn(len: uint, f: fn(index: uint) -> bool) -> Bitv {
-    let bitv = Bitv(len, false);
+    let mut bitv = Bitv::new(len, false);
     for uint::range(0, len) |i| {
         bitv.set(i, f(i));
     }
@@ -586,10 +584,10 @@ mod tests {
 
     #[test]
     pub fn test_to_str() {
-        let zerolen = Bitv(0u, false);
+        let zerolen = Bitv::new(0u, false);
         assert zerolen.to_str() == ~"";
 
-        let eightbits = Bitv(8u, false);
+        let eightbits = Bitv::new(8u, false);
         assert eightbits.to_str() == ~"00000000";
     }
 
@@ -597,7 +595,7 @@ mod tests {
     pub fn test_0_elements() {
         let mut act;
         let mut exp;
-        act = Bitv(0u, false);
+        act = Bitv::new(0u, false);
         exp = vec::from_elem::<uint>(0u, 0u);
         assert act.eq_vec(exp);
     }
@@ -605,15 +603,15 @@ mod tests {
     #[test]
     pub fn test_1_element() {
         let mut act;
-        act = Bitv(1u, false);
+        act = Bitv::new(1u, false);
         assert act.eq_vec(~[0u]);
-        act = Bitv(1u, true);
+        act = Bitv::new(1u, true);
         assert act.eq_vec(~[1u]);
     }
 
     #[test]
     pub fn test_2_elements() {
-        let b = bitv::Bitv(2, false);
+        let mut b = bitv::Bitv::new(2, false);
         b.set(0, true);
         b.set(1, false);
         assert b.to_str() == ~"10";
@@ -624,15 +622,15 @@ mod tests {
         let mut act;
         // all 0
 
-        act = Bitv(10u, false);
+        act = Bitv::new(10u, false);
         assert (act.eq_vec(~[0u, 0u, 0u, 0u, 0u, 0u, 0u, 0u, 0u, 0u]));
         // all 1
 
-        act = Bitv(10u, true);
+        act = Bitv::new(10u, true);
         assert (act.eq_vec(~[1u, 1u, 1u, 1u, 1u, 1u, 1u, 1u, 1u, 1u]));
         // mixed
 
-        act = Bitv(10u, false);
+        act = Bitv::new(10u, false);
         act.set(0u, true);
         act.set(1u, true);
         act.set(2u, true);
@@ -641,7 +639,7 @@ mod tests {
         assert (act.eq_vec(~[1u, 1u, 1u, 1u, 1u, 0u, 0u, 0u, 0u, 0u]));
         // mixed
 
-        act = Bitv(10u, false);
+        act = Bitv::new(10u, false);
         act.set(5u, true);
         act.set(6u, true);
         act.set(7u, true);
@@ -650,7 +648,7 @@ mod tests {
         assert (act.eq_vec(~[0u, 0u, 0u, 0u, 0u, 1u, 1u, 1u, 1u, 1u]));
         // mixed
 
-        act = Bitv(10u, false);
+        act = Bitv::new(10u, false);
         act.set(0u, true);
         act.set(3u, true);
         act.set(6u, true);
@@ -663,21 +661,21 @@ mod tests {
         let mut act;
         // all 0
 
-        act = Bitv(31u, false);
+        act = Bitv::new(31u, false);
         assert (act.eq_vec(
                        ~[0u, 0u, 0u, 0u, 0u, 0u, 0u, 0u, 0u, 0u, 0u, 0u, 0u,
                         0u, 0u, 0u, 0u, 0u, 0u, 0u, 0u, 0u, 0u, 0u, 0u, 0u,
                         0u, 0u, 0u, 0u, 0u]));
         // all 1
 
-        act = Bitv(31u, true);
+        act = Bitv::new(31u, true);
         assert (act.eq_vec(
                        ~[1u, 1u, 1u, 1u, 1u, 1u, 1u, 1u, 1u, 1u, 1u, 1u, 1u,
                         1u, 1u, 1u, 1u, 1u, 1u, 1u, 1u, 1u, 1u, 1u, 1u, 1u,
                         1u, 1u, 1u, 1u, 1u]));
         // mixed
 
-        act = Bitv(31u, false);
+        act = Bitv::new(31u, false);
         act.set(0u, true);
         act.set(1u, true);
         act.set(2u, true);
@@ -692,7 +690,7 @@ mod tests {
                         0u, 0u, 0u, 0u, 0u]));
         // mixed
 
-        act = Bitv(31u, false);
+        act = Bitv::new(31u, false);
         act.set(16u, true);
         act.set(17u, true);
         act.set(18u, true);
@@ -707,7 +705,7 @@ mod tests {
                         0u, 0u, 0u, 0u, 0u]));
         // mixed
 
-        act = Bitv(31u, false);
+        act = Bitv::new(31u, false);
         act.set(24u, true);
         act.set(25u, true);
         act.set(26u, true);
@@ -721,7 +719,7 @@ mod tests {
                         1u, 1u, 1u, 1u, 1u]));
         // mixed
 
-        act = Bitv(31u, false);
+        act = Bitv::new(31u, false);
         act.set(3u, true);
         act.set(17u, true);
         act.set(30u, true);
@@ -736,21 +734,21 @@ mod tests {
         let mut act;
         // all 0
 
-        act = Bitv(32u, false);
+        act = Bitv::new(32u, false);
         assert (act.eq_vec(
                        ~[0u, 0u, 0u, 0u, 0u, 0u, 0u, 0u, 0u, 0u, 0u, 0u, 0u,
                         0u, 0u, 0u, 0u, 0u, 0u, 0u, 0u, 0u, 0u, 0u, 0u, 0u,
                         0u, 0u, 0u, 0u, 0u, 0u]));
         // all 1
 
-        act = Bitv(32u, true);
+        act = Bitv::new(32u, true);
         assert (act.eq_vec(
                        ~[1u, 1u, 1u, 1u, 1u, 1u, 1u, 1u, 1u, 1u, 1u, 1u, 1u,
                         1u, 1u, 1u, 1u, 1u, 1u, 1u, 1u, 1u, 1u, 1u, 1u, 1u,
                         1u, 1u, 1u, 1u, 1u, 1u]));
         // mixed
 
-        act = Bitv(32u, false);
+        act = Bitv::new(32u, false);
         act.set(0u, true);
         act.set(1u, true);
         act.set(2u, true);
@@ -765,7 +763,7 @@ mod tests {
                         0u, 0u, 0u, 0u, 0u, 0u]));
         // mixed
 
-        act = Bitv(32u, false);
+        act = Bitv::new(32u, false);
         act.set(16u, true);
         act.set(17u, true);
         act.set(18u, true);
@@ -780,7 +778,7 @@ mod tests {
                         0u, 0u, 0u, 0u, 0u, 0u]));
         // mixed
 
-        act = Bitv(32u, false);
+        act = Bitv::new(32u, false);
         act.set(24u, true);
         act.set(25u, true);
         act.set(26u, true);
@@ -795,7 +793,7 @@ mod tests {
                         1u, 1u, 1u, 1u, 1u, 1u]));
         // mixed
 
-        act = Bitv(32u, false);
+        act = Bitv::new(32u, false);
         act.set(3u, true);
         act.set(17u, true);
         act.set(30u, true);
@@ -811,21 +809,21 @@ mod tests {
         let mut act;
         // all 0
 
-        act = Bitv(33u, false);
+        act = Bitv::new(33u, false);
         assert (act.eq_vec(
                        ~[0u, 0u, 0u, 0u, 0u, 0u, 0u, 0u, 0u, 0u, 0u, 0u, 0u,
                         0u, 0u, 0u, 0u, 0u, 0u, 0u, 0u, 0u, 0u, 0u, 0u, 0u,
                         0u, 0u, 0u, 0u, 0u, 0u, 0u]));
         // all 1
 
-        act = Bitv(33u, true);
+        act = Bitv::new(33u, true);
         assert (act.eq_vec(
                        ~[1u, 1u, 1u, 1u, 1u, 1u, 1u, 1u, 1u, 1u, 1u, 1u, 1u,
                         1u, 1u, 1u, 1u, 1u, 1u, 1u, 1u, 1u, 1u, 1u, 1u, 1u,
                         1u, 1u, 1u, 1u, 1u, 1u, 1u]));
         // mixed
 
-        act = Bitv(33u, false);
+        act = Bitv::new(33u, false);
         act.set(0u, true);
         act.set(1u, true);
         act.set(2u, true);
@@ -840,7 +838,7 @@ mod tests {
                         0u, 0u, 0u, 0u, 0u, 0u, 0u]));
         // mixed
 
-        act = Bitv(33u, false);
+        act = Bitv::new(33u, false);
         act.set(16u, true);
         act.set(17u, true);
         act.set(18u, true);
@@ -855,7 +853,7 @@ mod tests {
                         0u, 0u, 0u, 0u, 0u, 0u, 0u]));
         // mixed
 
-        act = Bitv(33u, false);
+        act = Bitv::new(33u, false);
         act.set(24u, true);
         act.set(25u, true);
         act.set(26u, true);
@@ -870,7 +868,7 @@ mod tests {
                         1u, 1u, 1u, 1u, 1u, 1u, 0u]));
         // mixed
 
-        act = Bitv(33u, false);
+        act = Bitv::new(33u, false);
         act.set(3u, true);
         act.set(17u, true);
         act.set(30u, true);
@@ -884,24 +882,24 @@ mod tests {
 
     #[test]
     pub fn test_equal_differing_sizes() {
-        let v0 = Bitv(10u, false);
-        let v1 = Bitv(11u, false);
+        let v0 = Bitv::new(10u, false);
+        let v1 = Bitv::new(11u, false);
         assert !v0.equal(&v1);
     }
 
     #[test]
     pub fn test_equal_greatly_differing_sizes() {
-        let v0 = Bitv(10u, false);
-        let v1 = Bitv(110u, false);
+        let v0 = Bitv::new(10u, false);
+        let v1 = Bitv::new(110u, false);
         assert !v0.equal(&v1);
     }
 
     #[test]
     pub fn test_equal_sneaky_small() {
-        let a = bitv::Bitv(1, false);
+        let mut a = bitv::Bitv::new(1, false);
         a.set(0, true);
 
-        let b = bitv::Bitv(1, true);
+        let mut b = bitv::Bitv::new(1, true);
         b.set(0, true);
 
         assert a.equal(&b);
@@ -909,12 +907,12 @@ mod tests {
 
     #[test]
     pub fn test_equal_sneaky_big() {
-        let a = bitv::Bitv(100, false);
+        let mut a = bitv::Bitv::new(100, false);
         for uint::range(0, 100) |i| {
             a.set(i, true);
         }
 
-        let b = bitv::Bitv(100, true);
+        let mut b = bitv::Bitv::new(100, true);
         for uint::range(0, 100) |i| {
             b.set(i, true);
         }
@@ -931,11 +929,11 @@ mod tests {
 
     #[test]
     pub fn test_to_bytes() {
-        let bv = Bitv(3, true);
+        let mut bv = Bitv::new(3, true);
         bv.set(1, false);
         assert bv.to_bytes() == ~[0b10100000];
 
-        let bv = Bitv(9, false);
+        let mut bv = Bitv::new(9, false);
         bv.set(2, true);
         bv.set(8, true);
         assert bv.to_bytes() == ~[0b00100000, 0b10000000];
@@ -954,8 +952,8 @@ mod tests {
 
     #[test]
     pub fn test_small_difference() {
-      let b1 = Bitv(3, false);
-      let b2 = Bitv(3, false);
+      let mut b1 = Bitv::new(3, false);
+      let mut b2 = Bitv::new(3, false);
       b1.set(0, true);
       b1.set(1, true);
       b2.set(1, true);
@@ -968,8 +966,8 @@ mod tests {
 
     #[test]
     pub fn test_big_difference() {
-      let b1 = Bitv(100, false);
-      let b2 = Bitv(100, false);
+      let mut b1 = Bitv::new(100, false);
+      let mut b2 = Bitv::new(100, false);
       b1.set(0, true);
       b1.set(40, true);
       b2.set(40, true);
@@ -982,7 +980,7 @@ mod tests {
 
     #[test]
     pub fn test_small_clear() {
-      let b = Bitv(14, true);
+      let mut b = Bitv::new(14, true);
       b.clear();
       for b.ones |i| {
           fail!(fmt!("found 1 at %?", i));
@@ -991,7 +989,7 @@ mod tests {
 
     #[test]
     pub fn test_big_clear() {
-      let b = Bitv(140, true);
+      let mut b = Bitv::new(140, true);
       b.clear();
       for b.ones |i| {
           fail!(fmt!("found 1 at %?", i));
diff --git a/src/libsyntax/ext/pipes/liveness.rs b/src/libsyntax/ext/pipes/liveness.rs
index c690c89c025f..a7f01d756485 100644
--- a/src/libsyntax/ext/pipes/liveness.rs
+++ b/src/libsyntax/ext/pipes/liveness.rs
@@ -43,13 +43,13 @@ use ext::base::ext_ctxt;
 use ext::pipes::proto::protocol;
 
 use core::str;
-use std::bitv::{Bitv};
+use std::bitv::Bitv;
 
 pub fn analyze(proto: protocol, _cx: ext_ctxt) {
     debug!("initializing colive analysis");
     let num_states = proto.num_states();
-    let colive = do (copy proto.states).map_to_vec |state| {
-        let bv = ~Bitv(num_states, false);
+    let mut colive = do (copy proto.states).map_to_vec |state| {
+        let mut bv = ~Bitv::new(num_states, false);
         for state.reachable |s| {
             bv.set(s.id, true);
         }
@@ -61,15 +61,19 @@ pub fn analyze(proto: protocol, _cx: ext_ctxt) {
     while changed {
         changed = false;
         debug!("colive iteration %?", i);
+        let mut new_colive = ~[];
         for colive.eachi |i, this_colive| {
+            let mut result = ~this_colive.clone();
             let this = proto.get_state_by_id(i);
             for this_colive.ones |j| {
                 let next = proto.get_state_by_id(j);
                 if this.dir == next.dir {
-                    changed = changed || this_colive.union(colive[j]);
+                    changed = result.union(colive[j]) || changed;
                 }
             }
+            new_colive.push(result)
         }
+        colive = new_colive;
         i += 1;
     }
 
diff --git a/src/test/bench/sudoku.rs b/src/test/bench/sudoku.rs
index 885eaf01c445..a3a3ef85f45a 100644
--- a/src/test/bench/sudoku.rs
+++ b/src/test/bench/sudoku.rs
@@ -58,7 +58,7 @@ pub fn solve_grid(g: grid_t) {
     fn next_color(mut g: grid, row: u8, col: u8, start_color: u8) -> bool {
         if start_color < 10u8 {
             // colors not yet used
-            let avail = bitv::Bitv(10u, false);
+            let mut avail = bitv::Bitv::new(10u, false);
             for u8::range(start_color, 10u8) |color| {
                 avail.set(color as uint, true);
             }
@@ -80,7 +80,7 @@ pub fn solve_grid(g: grid_t) {
 
     // find colors available in neighbourhood of (row, col)
     fn drop_colors(g: grid, avail: bitv::Bitv, row: u8, col: u8) {
-        fn drop_color(g: grid, colors: bitv::Bitv, row: u8, col: u8) {
+        fn drop_color(g: grid, mut colors: bitv::Bitv, row: u8, col: u8) {
             let color = g[row][col];
             if color != 0u8 { colors.set(color as uint, false); }
         }
diff --git a/src/test/run-pass/bitv-perf-test.rs b/src/test/run-pass/bitv-perf-test.rs
index 097db4436fdb..6cb0cf4e3776 100644
--- a/src/test/run-pass/bitv-perf-test.rs
+++ b/src/test/run-pass/bitv-perf-test.rs
@@ -14,8 +14,8 @@ extern mod std;
 use std::bitv::*;
 
 fn bitv_test() -> bool {
-    let v1 = ~Bitv(31, false);
-    let v2 = ~Bitv(31, true);
+    let mut v1 = ~Bitv::new(31, false);
+    let v2 = ~Bitv::new(31, true);
     v1.union(v2);
     true
 }