Move checked arithmetic operators into Int trait

20 files changed, 324 insertions, 371 deletions

diff --git a/src/etc/vim/syntax/rust.vim b/src/etc/vim/syntax/rust.vim
index 0ef9734cf2e..7033f493f0f 100644
--- a/src/etc/vim/syntax/rust.vim
+++ b/src/etc/vim/syntax/rust.vim
@@ -97,7 +97,7 @@ syn keyword rustTrait FromIterator IntoIterator Extend ExactSize
 syn keyword rustTrait Iterator DoubleEndedIterator
 syn keyword rustTrait RandomAccessIterator CloneableIterator
 syn keyword rustTrait OrdIterator MutableDoubleEndedIterator
-syn keyword rustTrait Num NumCast CheckedAdd CheckedSub CheckedMul CheckedDiv
+syn keyword rustTrait Num NumCast
 syn keyword rustTrait Signed Unsigned Primitive Int Float
 syn keyword rustTrait FloatMath ToPrimitive FromPrimitive
 syn keyword rustTrait Box
diff --git a/src/libarena/lib.rs b/src/libarena/lib.rs
index fb091ec7f84..1e9ab34b0ac 100644
--- a/src/libarena/lib.rs
+++ b/src/libarena/lib.rs
@@ -132,7 +132,7 @@ impl Drop for Arena {
 
 #[inline]
 fn round_up(base: uint, align: uint) -> uint {
-    (base.checked_add(&(align - 1))).unwrap() & !(align - 1)
+    (base.checked_add(align - 1)).unwrap() & !(align - 1)
 }
 
 // Walk down a chunk, running the destructors for any objects stored
@@ -376,8 +376,8 @@ fn calculate_size<T>(capacity: uint) -> uint {
     let mut size = mem::size_of::<TypedArenaChunk<T>>();
     size = round_up(size, mem::min_align_of::<T>());
     let elem_size = mem::size_of::<T>();
-    let elems_size = elem_size.checked_mul(&capacity).unwrap();
-    size = size.checked_add(&elems_size).unwrap();
+    let elems_size = elem_size.checked_mul(capacity).unwrap();
+    size = size.checked_add(elems_size).unwrap();
     size
 }
 
@@ -432,7 +432,7 @@ impl<T> TypedArenaChunk<T> {
     #[inline]
     fn end(&self) -> *const u8 {
         unsafe {
-            let size = mem::size_of::<T>().checked_mul(&self.capacity).unwrap();
+            let size = mem::size_of::<T>().checked_mul(self.capacity).unwrap();
             self.start().offset(size as int)
         }
     }
@@ -481,7 +481,7 @@ impl<T> TypedArena<T> {
     fn grow(&self) {
         unsafe {
             let chunk = *self.first.borrow_mut();
-            let new_capacity = (*chunk).capacity.checked_mul(&2).unwrap();
+            let new_capacity = (*chunk).capacity.checked_mul(2).unwrap();
             let chunk = TypedArenaChunk::<T>::new(chunk, new_capacity);
             self.ptr.set((*chunk).start() as *const T);
             self.end.set((*chunk).end() as *const T);
diff --git a/src/libcollections/vec.rs b/src/libcollections/vec.rs
index 3ef7667dd8f..9f51c6d1b5e 100644
--- a/src/libcollections/vec.rs
+++ b/src/libcollections/vec.rs
@@ -161,7 +161,7 @@ impl<T> Vec<T> {
         } else if capacity == 0 {
             Vec::new()
         } else {
-            let size = capacity.checked_mul(&mem::size_of::<T>())
+            let size = capacity.checked_mul(mem::size_of::<T>())
                                .expect("capacity overflow");
             let ptr = unsafe { allocate(size, mem::min_align_of::<T>()) };
             Vec { ptr: ptr as *mut T, len: 0, cap: capacity }
@@ -601,7 +601,7 @@ impl<T> Vec<T> {
     #[unstable = "matches collection reform specification, waiting for dust to settle"]
     pub fn reserve(&mut self, additional: uint) {
         if self.cap - self.len < additional {
-            match self.len.checked_add(&additional) {
+            match self.len.checked_add(additional) {
                 None => panic!("Vec::reserve: `uint` overflow"),
                 // if the checked_add
                 Some(new_cap) => {
@@ -638,7 +638,7 @@ impl<T> Vec<T> {
     #[unstable = "matches collection reform specification, waiting for dust to settle"]
     pub fn reserve_exact(&mut self, additional: uint) {
         if self.cap - self.len < additional {
-            match self.len.checked_add(&additional) {
+            match self.len.checked_add(additional) {
                 None => panic!("Vec::reserve: `uint` overflow"),
                 Some(new_cap) => self.grow_capacity(new_cap)
             }
@@ -971,7 +971,7 @@ impl<T> Vec<T> {
     pub fn push(&mut self, value: T) {
         if mem::size_of::<T>() == 0 {
             // zero-size types consume no memory, so we can't rely on the address space running out
-            self.len = self.len.checked_add(&1).expect("length overflow");
+            self.len = self.len.checked_add(1).expect("length overflow");
             unsafe { mem::forget(value); }
             return
         }
@@ -1064,7 +1064,7 @@ impl<T> Vec<T> {
         if mem::size_of::<T>() == 0 { return }
 
         if capacity > self.cap {
-            let size = capacity.checked_mul(&mem::size_of::<T>())
+            let size = capacity.checked_mul(mem::size_of::<T>())
                                .expect("capacity overflow");
             unsafe {
                 self.ptr = alloc_or_realloc(self.ptr, self.cap * mem::size_of::<T>(), size);
diff --git a/src/libcore/iter.rs b/src/libcore/iter.rs
index 73d3aef5ee0..0effc4b19dc 100644
--- a/src/libcore/iter.rs
+++ b/src/libcore/iter.rs
@@ -60,9 +60,9 @@ This `for` loop syntax can be applied to any iterator over any type.
 
 use clone::Clone;
 use cmp;
-use cmp::{PartialEq, PartialOrd, Ord};
+use cmp::{PartialOrd, Ord};
 use mem;
-use num::{Zero, One, CheckedAdd, CheckedSub, ToPrimitive, Int};
+use num::{Zero, One, ToPrimitive, Int};
 use ops::{Add, Mul, Sub};
 use option::{Option, Some, None};
 use uint;
@@ -1093,7 +1093,7 @@ impl<A, T: Iterator<A>, U: Iterator<A>> Iterator<A> for Chain<T, U> {
         let lower = a_lower.saturating_add(b_lower);
 
         let upper = match (a_upper, b_upper) {
-            (Some(x), Some(y)) => x.checked_add(&y),
+            (Some(x), Some(y)) => x.checked_add(y),
             _ => None
         };
 
@@ -1415,7 +1415,7 @@ impl<A, T: Iterator<A>> Iterator<A> for Peekable<A, T> {
         if self.peeked.is_some() {
             let lo = lo.saturating_add(1);
             let hi = match hi {
-                Some(x) => x.checked_add(&1),
+                Some(x) => x.checked_add(1),
                 None => None
             };
             (lo, hi)
@@ -1680,7 +1680,7 @@ impl<'a, A, T: Iterator<A>, B, U: Iterator<B>> Iterator<B> for FlatMap<'a, A, T,
         let (blo, bhi) = self.backiter.as_ref().map_or((0, Some(0)), |it| it.size_hint());
         let lo = flo.saturating_add(blo);
         match (self.iter.size_hint(), fhi, bhi) {
-            ((0, Some(0)), Some(a), Some(b)) => (lo, a.checked_add(&b)),
+            ((0, Some(0)), Some(a), Some(b)) => (lo, a.checked_add(b)),
             _ => (lo, None)
         }
     }
@@ -1946,7 +1946,7 @@ impl<A: Add<A, A> + PartialOrd + Clone + ToPrimitive> Iterator<A> for Range<A> {
         // the i64/u64 might lie within their range.
         let bound = match self.state.to_i64() {
             Some(a) => {
-                let sz = self.stop.to_i64().map(|b| b.checked_sub(&a));
+                let sz = self.stop.to_i64().map(|b| b.checked_sub(a));
                 match sz {
                     Some(Some(bound)) => bound.to_uint(),
                     _ => None,
@@ -1954,7 +1954,7 @@ impl<A: Add<A, A> + PartialOrd + Clone + ToPrimitive> Iterator<A> for Range<A> {
             },
             None => match self.state.to_u64() {
                 Some(a) => {
-                    let sz = self.stop.to_u64().map(|b| b.checked_sub(&a));
+                    let sz = self.stop.to_u64().map(|b| b.checked_sub(a));
                     match sz {
                         Some(Some(bound)) => bound.to_uint(),
                         _ => None
@@ -2024,7 +2024,7 @@ impl<A: Add<A, A> + PartialOrd + Clone + ToPrimitive> Iterator<A> for RangeInclu
         } else {
             let lo = lo.saturating_add(1);
             let hi = match hi {
-                Some(x) => x.checked_add(&1),
+                Some(x) => x.checked_add(1),
                 None => None
             };
             (lo, hi)
@@ -2060,18 +2060,17 @@ pub struct RangeStep<A> {
 
 /// Return an iterator over the range [start, stop) by `step`. It handles overflow by stopping.
 #[inline]
-pub fn range_step<A: CheckedAdd + PartialOrd +
-                  Clone + Zero>(start: A, stop: A, step: A) -> RangeStep<A> {
+pub fn range_step<A: Int>(start: A, stop: A, step: A) -> RangeStep<A> {
     let rev = step < Zero::zero();
     RangeStep{state: start, stop: stop, step: step, rev: rev}
 }
 
-impl<A: CheckedAdd + PartialOrd + Clone> Iterator<A> for RangeStep<A> {
+impl<A: Int> Iterator<A> for RangeStep<A> {
     #[inline]
     fn next(&mut self) -> Option<A> {
         if (self.rev && self.state > self.stop) || (!self.rev && self.state < self.stop) {
-            let result = self.state.clone();
-            match self.state.checked_add(&self.step) {
+            let result = self.state;
+            match self.state.checked_add(self.step) {
                 Some(x) => self.state = x,
                 None => self.state = self.stop.clone()
             }
@@ -2094,19 +2093,18 @@ pub struct RangeStepInclusive<A> {
 
 /// Return an iterator over the range [start, stop] by `step`. It handles overflow by stopping.
 #[inline]
-pub fn range_step_inclusive<A: CheckedAdd + PartialOrd + Clone + Zero>(start: A, stop: A,
-                                                                step: A) -> RangeStepInclusive<A> {
+pub fn range_step_inclusive<A: Int>(start: A, stop: A, step: A) -> RangeStepInclusive<A> {
     let rev = step < Zero::zero();
     RangeStepInclusive{state: start, stop: stop, step: step, rev: rev, done: false}
 }
 
-impl<A: CheckedAdd + PartialOrd + Clone + PartialEq> Iterator<A> for RangeStepInclusive<A> {
+impl<A: Int> Iterator<A> for RangeStepInclusive<A> {
     #[inline]
     fn next(&mut self) -> Option<A> {
         if !self.done && ((self.rev && self.state >= self.stop) ||
                           (!self.rev && self.state <= self.stop)) {
-            let result = self.state.clone();
-            match self.state.checked_add(&self.step) {
+            let result = self.state;
+            match self.state.checked_add(self.step) {
                 Some(x) => self.state = x,
                 None => self.done = true
             }
diff --git a/src/libcore/num/mod.rs b/src/libcore/num/mod.rs
index 9726b7b3978..b26e8dd83fe 100644
--- a/src/libcore/num/mod.rs
+++ b/src/libcore/num/mod.rs
@@ -348,10 +348,6 @@ trait_impl!(Primitive for uint u8 u16 u32 u64 int i8 i16 i32 i64 f32 f64)
 /// operators, bit counting methods, and endian conversion functions.
 pub trait Int: Primitive
              + Ord
-             + CheckedAdd
-             + CheckedSub
-             + CheckedMul
-             + CheckedDiv
              + Bounded
              + Not<Self>
              + BitAnd<Self,Self>
@@ -526,11 +522,65 @@ pub trait Int: Primitive
         if cfg!(target_endian = "little") { self } else { self.swap_bytes() }
     }
 
+    /// Adds two numbers, checking for overflow. If overflow occurs, `None` is
+    /// returned.
+    ///
+    /// # Example
+    ///
+    /// ```rust
+    /// use std::num::Int;
+    ///
+    /// assert_eq!(5u16.checked_add(65530), Some(65535));
+    /// assert_eq!(6u16.checked_add(65530), None);
+    /// ```
+    fn checked_add(self, other: Self) -> Option<Self>;
+
+    /// Subtracts two numbers, checking for underflow. If underflow occurs,
+    /// `None` is returned.
+    ///
+    /// # Example
+    ///
+    /// ```rust
+    /// use std::num::Int;
+    ///
+    /// assert_eq!((-127i8).checked_sub(1), Some(-128));
+    /// assert_eq!((-128i8).checked_sub(1), None);
+    /// ```
+    fn checked_sub(self, other: Self) -> Option<Self>;
+
+    /// Multiplies two numbers, checking for underflow or overflow. If underflow
+    /// or overflow occurs, `None` is returned.
+    ///
+    /// # Example
+    ///
+    /// ```rust
+    /// use std::num::Int;
+    ///
+    /// assert_eq!(5u8.checked_mul(51), Some(255));
+    /// assert_eq!(5u8.checked_mul(52), None);
+    /// ```
+    fn checked_mul(self, other: Self) -> Option<Self>;
+
+    /// Divides two numbers, checking for underflow, overflow and division by
+    /// zero. If underflow occurs, `None` is returned.
+    ///
+    /// # Example
+    ///
+    /// ```rust
+    /// use std::num::Int;
+    ///
+    /// assert_eq!((-127i8).checked_div(-1), Some(127));
+    /// assert_eq!((-128i8).checked_div(-1), None);
+    /// assert_eq!((1i8).checked_div(0), None);
+    /// ```
+    #[inline]
+    fn checked_div(self, other: Self) -> Option<Self>;
+
     /// Saturating addition. Returns `self + other`, saturating at the
     /// numeric bounds instead of overflowing.
     #[inline]
     fn saturating_add(self, other: Self) -> Self {
-        match self.checked_add(&other) {
+        match self.checked_add(other) {
             Some(x)                       => x,
             None if other >= Zero::zero() => Bounded::max_value(),
             None                          => Bounded::min_value(),
@@ -541,7 +591,7 @@ pub trait Int: Primitive
     /// numeric bounds instead of overflowing.
     #[inline]
     fn saturating_sub(self, other: Self) -> Self {
-        match self.checked_sub(&other) {
+        match self.checked_sub(other) {
             Some(x)                       => x,
             None if other >= Zero::zero() => Bounded::min_value(),
             None                          => Bounded::max_value(),
@@ -549,9 +599,22 @@ pub trait Int: Primitive
     }
 }
 
+macro_rules! checked_op {
+    ($T:ty, $U:ty, $op:path, $x:expr, $y:expr) => {{
+        let (result, overflowed) = unsafe { $op($x as $U, $y as $U) };
+        if overflowed { None } else { Some(result as $T) }
+    }}
+}
+
 macro_rules! uint_impl {
-    ($T:ty, $ActualT:ty, $BITS:expr,
-     $ctpop:path, $ctlz:path, $cttz:path, $bswap:path) => {
+    ($T:ty = $ActualT:ty, $BITS:expr,
+     $ctpop:path,
+     $ctlz:path,
+     $cttz:path,
+     $bswap:path,
+     $add_with_overflow:path,
+     $sub_with_overflow:path,
+     $mul_with_overflow:path) => {
         impl Int for $T {
             #[inline]
             fn count_ones(self) -> uint { unsafe { $ctpop(self as $ActualT) as uint } }
@@ -578,6 +641,29 @@ macro_rules! uint_impl {
 
             #[inline]
             fn swap_bytes(self) -> $T { unsafe { $bswap(self as $ActualT) as $T } }
+
+            #[inline]
+            fn checked_add(self, other: $T) -> Option<$T> {
+                checked_op!($T, $ActualT, $add_with_overflow, self, other)
+            }
+
+            #[inline]
+            fn checked_sub(self, other: $T) -> Option<$T> {
+                checked_op!($T, $ActualT, $sub_with_overflow, self, other)
+            }
+
+            #[inline]
+            fn checked_mul(self, other: $T) -> Option<$T> {
+                checked_op!($T, $ActualT, $mul_with_overflow, self, other)
+            }
+
+            #[inline]
+            fn checked_div(self, v: $T) -> Option<$T> {
+                match v {
+                    0 => None,
+                    v => Some(self / v),
+                }
+            }
         }
     }
 }
@@ -586,74 +672,145 @@ macro_rules! uint_impl {
 /// consistency with the other `bswap` intrinsics.
 unsafe fn bswap8(x: u8) -> u8 { x }
 
-uint_impl!(u8, u8, 8,
+uint_impl!(u8 = u8, 8,
     intrinsics::ctpop8,
     intrinsics::ctlz8,
     intrinsics::cttz8,
-    bswap8)
+    bswap8,
+    intrinsics::u8_add_with_overflow,
+    intrinsics::u8_sub_with_overflow,
+    intrinsics::u8_mul_with_overflow)
 
-uint_impl!(u16, u16, 16,
+uint_impl!(u16 = u16, 16,
     intrinsics::ctpop16,
     intrinsics::ctlz16,
     intrinsics::cttz16,
-    intrinsics::bswap16)
+    intrinsics::bswap16,
+    intrinsics::u16_add_with_overflow,
+    intrinsics::u16_sub_with_overflow,
+    intrinsics::u16_mul_with_overflow)
 
-uint_impl!(u32, u32, 32,
+uint_impl!(u32 = u32, 32,
     intrinsics::ctpop32,
     intrinsics::ctlz32,
     intrinsics::cttz32,
-    intrinsics::bswap32)
+    intrinsics::bswap32,
+    intrinsics::u32_add_with_overflow,
+    intrinsics::u32_sub_with_overflow,
+    intrinsics::u32_mul_with_overflow)
 
-uint_impl!(u64, u64, 64,
+uint_impl!(u64 = u64, 64,
     intrinsics::ctpop64,
     intrinsics::ctlz64,
     intrinsics::cttz64,
-    intrinsics::bswap64)
+    intrinsics::bswap64,
+    intrinsics::u64_add_with_overflow,
+    intrinsics::u64_sub_with_overflow,
+    intrinsics::u64_mul_with_overflow)
 
 #[cfg(target_word_size = "32")]
-uint_impl!(uint, u32, 32,
+uint_impl!(uint = u32, 32,
     intrinsics::ctpop32,
     intrinsics::ctlz32,
     intrinsics::cttz32,
-    intrinsics::bswap32)
+    intrinsics::bswap32,
+    intrinsics::u32_add_with_overflow,
+    intrinsics::u32_sub_with_overflow,
+    intrinsics::u32_mul_with_overflow)
 
 #[cfg(target_word_size = "64")]
-uint_impl!(uint, u64, 64,
+uint_impl!(uint = u64, 64,
     intrinsics::ctpop64,
     intrinsics::ctlz64,
     intrinsics::cttz64,
-    intrinsics::bswap64)
+    intrinsics::bswap64,
+    intrinsics::u64_add_with_overflow,
+    intrinsics::u64_sub_with_overflow,
+    intrinsics::u64_mul_with_overflow)
 
 macro_rules! int_impl {
-    ($T:ty, $U:ty) => {
+    ($T:ty = $ActualT:ty, $UnsignedT:ty,
+     $add_with_overflow:path,
+     $sub_with_overflow:path,
+     $mul_with_overflow:path) => {
         impl Int for $T {
             #[inline]
-            fn count_ones(self) -> uint { (self as $U).count_ones() }
+            fn count_ones(self) -> uint { (self as $UnsignedT).count_ones() }
 
             #[inline]
-            fn leading_zeros(self) -> uint { (self as $U).leading_zeros() }
+            fn leading_zeros(self) -> uint { (self as $UnsignedT).leading_zeros() }
 
             #[inline]
-            fn trailing_zeros(self) -> uint { (self as $U).trailing_zeros() }
+            fn trailing_zeros(self) -> uint { (self as $UnsignedT).trailing_zeros() }
 
             #[inline]
-            fn rotate_left(self, n: uint) -> $T { (self as $U).rotate_left(n) as $T }
+            fn rotate_left(self, n: uint) -> $T { (self as $UnsignedT).rotate_left(n) as $T }
 
             #[inline]
-            fn rotate_right(self, n: uint) -> $T { (self as $U).rotate_right(n) as $T }
+            fn rotate_right(self, n: uint) -> $T { (self as $UnsignedT).rotate_right(n) as $T }
 
             #[inline]
-            fn swap_bytes(self) -> $T { (self as $U).swap_bytes() as $T }
+            fn swap_bytes(self) -> $T { (self as $UnsignedT).swap_bytes() as $T }
+
+            #[inline]
+            fn checked_add(self, other: $T) -> Option<$T> {
+                checked_op!($T, $ActualT, $add_with_overflow, self, other)
+            }
+
+            #[inline]
+            fn checked_sub(self, other: $T) -> Option<$T> {
+                checked_op!($T, $ActualT, $sub_with_overflow, self, other)
+            }
+
+            #[inline]
+            fn checked_mul(self, other: $T) -> Option<$T> {
+                checked_op!($T, $ActualT, $mul_with_overflow, self, other)
+            }
+
+            #[inline]
+            fn checked_div(self, v: $T) -> Option<$T> {
+                match v {
+                    0   => None,
+                   -1 if self == Bounded::min_value()
+                        => None,
+                    v   => Some(self / v),
+                }
+            }
         }
     }
 }
 
-int_impl!(i8, u8)
-int_impl!(i16, u16)
-int_impl!(i32, u32)
-int_impl!(i64, u64)
-#[cfg(target_word_size = "32")] int_impl!(int, u32)
-#[cfg(target_word_size = "64")] int_impl!(int, u64)
+int_impl!(i8 = i8, u8,
+    intrinsics::i8_add_with_overflow,
+    intrinsics::i8_sub_with_overflow,
+    intrinsics::i8_mul_with_overflow)
+
+int_impl!(i16 = i16, u16,
+    intrinsics::i16_add_with_overflow,
+    intrinsics::i16_sub_with_overflow,
+    intrinsics::i16_mul_with_overflow)
+
+int_impl!(i32 = i32, u32,
+    intrinsics::i32_add_with_overflow,
+    intrinsics::i32_sub_with_overflow,
+    intrinsics::i32_mul_with_overflow)
+
+int_impl!(i64 = i64, u64,
+    intrinsics::i64_add_with_overflow,
+    intrinsics::i64_sub_with_overflow,
+    intrinsics::i64_mul_with_overflow)
+
+#[cfg(target_word_size = "32")]
+int_impl!(int = i32, u32,
+    intrinsics::i32_add_with_overflow,
+    intrinsics::i32_sub_with_overflow,
+    intrinsics::i32_mul_with_overflow)
+
+#[cfg(target_word_size = "64")]
+int_impl!(int = i64, u64,
+    intrinsics::i64_add_with_overflow,
+    intrinsics::i64_sub_with_overflow,
+    intrinsics::i64_mul_with_overflow)
 
 /// Unsigned integers
 pub trait UnsignedInt: Int {
@@ -686,7 +843,7 @@ pub trait UnsignedInt: Int {
             tmp = tmp | (tmp >> shift);
             shift = shift << 1u;
         }
-        tmp.checked_add(&one())
+        tmp.checked_add(one())
     }
 }
 
@@ -1184,192 +1341,6 @@ impl_num_cast!(int,   to_int)
 impl_num_cast!(f32,   to_f32)
 impl_num_cast!(f64,   to_f64)
 
-/// Performs addition that returns `None` instead of wrapping around on overflow.
-pub trait CheckedAdd: Add<Self, Self> {
-    /// Adds two numbers, checking for overflow. If overflow happens, `None` is returned.
-    ///
-    /// # Example
-    ///
-    /// ```rust
-    /// use std::num::CheckedAdd;
-    /// assert_eq!(5u16.checked_add(&65530), Some(65535));
-    /// assert_eq!(6u16.checked_add(&65530), None);
-    /// ```
-    fn checked_add(&self, v: &Self) -> Option<Self>;
-}
-
-macro_rules! checked_impl(
-    ($trait_name:ident, $method:ident, $t:ty, $op:path) => {
-        impl $trait_name for $t {
-            #[inline]
-            fn $method(&self, v: &$t) -> Option<$t> {
-                unsafe {
-                    let (x, y) = $op(*self, *v);
-                    if y { None } else { Some(x) }
-                }
-            }
-        }
-    }
-)
-macro_rules! checked_cast_impl(
-    ($trait_name:ident, $method:ident, $t:ty, $cast:ty, $op:path) => {
-        impl $trait_name for $t {
-            #[inline]
-            fn $method(&self, v: &$t) -> Option<$t> {
-                unsafe {
-                    let (x, y) = $op(*self as $cast, *v as $cast);
-                    if y { None } else { Some(x as $t) }
-                }
-            }
-        }
-    }
-)
-
-#[cfg(target_word_size = "32")]
-checked_cast_impl!(CheckedAdd, checked_add, uint, u32, intrinsics::u32_add_with_overflow)
-#[cfg(target_word_size = "64")]
-checked_cast_impl!(CheckedAdd, checked_add, uint, u64, intrinsics::u64_add_with_overflow)
-
-checked_impl!(CheckedAdd, checked_add, u8,  intrinsics::u8_add_with_overflow)
-checked_impl!(CheckedAdd, checked_add, u16, intrinsics::u16_add_with_overflow)
-checked_impl!(CheckedAdd, checked_add, u32, intrinsics::u32_add_with_overflow)
-checked_impl!(CheckedAdd, checked_add, u64, intrinsics::u64_add_with_overflow)
-
-#[cfg(target_word_size = "32")]
-checked_cast_impl!(CheckedAdd, checked_add, int, i32, intrinsics::i32_add_with_overflow)
-#[cfg(target_word_size = "64")]
-checked_cast_impl!(CheckedAdd, checked_add, int, i64, intrinsics::i64_add_with_overflow)
-
-checked_impl!(CheckedAdd, checked_add, i8,  intrinsics::i8_add_with_overflow)
-checked_impl!(CheckedAdd, checked_add, i16, intrinsics::i16_add_with_overflow)
-checked_impl!(CheckedAdd, checked_add, i32, intrinsics::i32_add_with_overflow)
-checked_impl!(CheckedAdd, checked_add, i64, intrinsics::i64_add_with_overflow)
-
-/// Performs subtraction that returns `None` instead of wrapping around on underflow.
-pub trait CheckedSub: Sub<Self, Self> {
-    /// Subtracts two numbers, checking for underflow. If underflow happens, `None` is returned.
-    ///
-    /// # Example
-    ///
-    /// ```rust
-    /// use std::num::CheckedSub;
-    /// assert_eq!((-127i8).checked_sub(&1), Some(-128));
-    /// assert_eq!((-128i8).checked_sub(&1), None);
-    /// ```
-    fn checked_sub(&self, v: &Self) -> Option<Self>;
-}
-
-#[cfg(target_word_size = "32")]
-checked_cast_impl!(CheckedSub, checked_sub, uint, u32, intrinsics::u32_sub_with_overflow)
-#[cfg(target_word_size = "64")]
-checked_cast_impl!(CheckedSub, checked_sub, uint, u64, intrinsics::u64_sub_with_overflow)
-
-checked_impl!(CheckedSub, checked_sub, u8,  intrinsics::u8_sub_with_overflow)
-checked_impl!(CheckedSub, checked_sub, u16, intrinsics::u16_sub_with_overflow)
-checked_impl!(CheckedSub, checked_sub, u32, intrinsics::u32_sub_with_overflow)
-checked_impl!(CheckedSub, checked_sub, u64, intrinsics::u64_sub_with_overflow)
-
-#[cfg(target_word_size = "32")]
-checked_cast_impl!(CheckedSub, checked_sub, int, i32, intrinsics::i32_sub_with_overflow)
-#[cfg(target_word_size = "64")]
-checked_cast_impl!(CheckedSub, checked_sub, int, i64, intrinsics::i64_sub_with_overflow)
-
-checked_impl!(CheckedSub, checked_sub, i8,  intrinsics::i8_sub_with_overflow)
-checked_impl!(CheckedSub, checked_sub, i16, intrinsics::i16_sub_with_overflow)
-checked_impl!(CheckedSub, checked_sub, i32, intrinsics::i32_sub_with_overflow)
-checked_impl!(CheckedSub, checked_sub, i64, intrinsics::i64_sub_with_overflow)
-
-/// Performs multiplication that returns `None` instead of wrapping around on underflow or
-/// overflow.
-pub trait CheckedMul: Mul<Self, Self> {
-    /// Multiplies two numbers, checking for underflow or overflow. If underflow or overflow
-    /// happens, `None` is returned.
-    ///
-    /// # Example
-    ///
-    /// ```rust
-    /// use std::num::CheckedMul;
-    /// assert_eq!(5u8.checked_mul(&51), Some(255));
-    /// assert_eq!(5u8.checked_mul(&52), None);
-    /// ```
-    fn checked_mul(&self, v: &Self) -> Option<Self>;
-}
-
-#[cfg(target_word_size = "32")]
-checked_cast_impl!(CheckedMul, checked_mul, uint, u32, intrinsics::u32_mul_with_overflow)
-#[cfg(target_word_size = "64")]
-checked_cast_impl!(CheckedMul, checked_mul, uint, u64, intrinsics::u64_mul_with_overflow)
-
-checked_impl!(CheckedMul, checked_mul, u8,  intrinsics::u8_mul_with_overflow)
-checked_impl!(CheckedMul, checked_mul, u16, intrinsics::u16_mul_with_overflow)
-checked_impl!(CheckedMul, checked_mul, u32, intrinsics::u32_mul_with_overflow)
-checked_impl!(CheckedMul, checked_mul, u64, intrinsics::u64_mul_with_overflow)
-
-#[cfg(target_word_size = "32")]
-checked_cast_impl!(CheckedMul, checked_mul, int, i32, intrinsics::i32_mul_with_overflow)
-#[cfg(target_word_size = "64")]
-checked_cast_impl!(CheckedMul, checked_mul, int, i64, intrinsics::i64_mul_with_overflow)
-
-checked_impl!(CheckedMul, checked_mul, i8,  intrinsics::i8_mul_with_overflow)
-checked_impl!(CheckedMul, checked_mul, i16, intrinsics::i16_mul_with_overflow)
-checked_impl!(CheckedMul, checked_mul, i32, intrinsics::i32_mul_with_overflow)
-checked_impl!(CheckedMul, checked_mul, i64, intrinsics::i64_mul_with_overflow)
-
-/// Performs division that returns `None` instead of panicking on division by zero and instead of
-/// wrapping around on underflow and overflow.
-pub trait CheckedDiv: Div<Self, Self> {
-    /// Divides two numbers, checking for underflow, overflow and division by zero. If any of that
-    /// happens, `None` is returned.
-    ///
-    /// # Example
-    ///
-    /// ```rust
-    /// use std::num::CheckedDiv;
-    /// assert_eq!((-127i8).checked_div(&-1), Some(127));
-    /// assert_eq!((-128i8).checked_div(&-1), None);
-    /// assert_eq!((1i8).checked_div(&0), None);
-    /// ```
-    fn checked_div(&self, v: &Self) -> Option<Self>;
-}
-
-macro_rules! checkeddiv_int_impl(
-    ($t:ty, $min:expr) => {
-        impl CheckedDiv for $t {
-            #[inline]
-            fn checked_div(&self, v: &$t) -> Option<$t> {
-                if *v == 0 || (*self == $min && *v == -1) {
-                    None
-                } else {
-                    Some(*self / *v)
-                }
-            }
-        }
-    }
-)
-
-checkeddiv_int_impl!(int, int::MIN)
-checkeddiv_int_impl!(i8, i8::MIN)
-checkeddiv_int_impl!(i16, i16::MIN)
-checkeddiv_int_impl!(i32, i32::MIN)
-checkeddiv_int_impl!(i64, i64::MIN)
-
-macro_rules! checkeddiv_uint_impl(
-    ($($t:ty)*) => ($(
-        impl CheckedDiv for $t {
-            #[inline]
-            fn checked_div(&self, v: &$t) -> Option<$t> {
-                if *v == 0 {
-                    None
-                } else {
-                    Some(*self / *v)
-                }
-            }
-        }
-    )*)
-)
-
-checkeddiv_uint_impl!(uint u8 u16 u32 u64)
-
 /// Used for representing the classification of floating point numbers
 #[deriving(PartialEq, Show)]
 pub enum FPCategory {
diff --git a/src/libcore/prelude.rs b/src/libcore/prelude.rs
index 17f7a04819f..045aca8aa0a 100644
--- a/src/libcore/prelude.rs
+++ b/src/libcore/prelude.rs
@@ -51,7 +51,7 @@ pub use cmp::{Ordering, Less, Equal, Greater, Equiv};
 pub use iter::{FromIterator, Extend};
 pub use iter::{Iterator, DoubleEndedIterator, RandomAccessIterator, CloneableIterator};
 pub use iter::{OrdIterator, MutableDoubleEndedIterator, ExactSize};
-pub use num::{Num, NumCast, CheckedAdd, CheckedSub, CheckedMul};
+pub use num::{Num, NumCast};
 pub use num::{Signed, Unsigned, Float};
 pub use num::{Primitive, Int, ToPrimitive, FromPrimitive};
 pub use option::{Option, Some, None};
diff --git a/src/libcore/slice.rs b/src/libcore/slice.rs
index fd01ed69f81..7b223dc501b 100644
--- a/src/libcore/slice.rs
+++ b/src/libcore/slice.rs
@@ -40,7 +40,7 @@ use cmp::{PartialEq, PartialOrd, Eq, Ord, Ordering, Less, Equal, Greater, Equiv}
 use cmp;
 use default::Default;
 use iter::*;
-use num::{CheckedAdd, Int, div_rem};
+use num::{Int, div_rem};
 use ops;
 use option::{None, Option, Some};
 use ptr;
@@ -1346,7 +1346,7 @@ impl<'a, T> Iterator<&'a [T]> for Windows<'a, T> {
             (0, Some(0))
         } else {
             let x = self.v.len() - self.size;
-            (x.saturating_add(1), x.checked_add(&1u))
+            (x.saturating_add(1), x.checked_add(1u))
         }
     }
 }
diff --git a/src/libcore/str.rs b/src/libcore/str.rs
index 3aee6867fd5..b3bed201598 100644
--- a/src/libcore/str.rs
+++ b/src/libcore/str.rs
@@ -25,7 +25,7 @@ use iter::{Map, Iterator};
 use iter::{DoubleEndedIterator, ExactSize};
 use iter::range;
 use kinds::Sized;
-use num::{CheckedMul, Int};
+use num::Int;
 use option::{Option, None, Some};
 use raw::Repr;
 use slice::{mod, SlicePrelude};
@@ -750,7 +750,7 @@ impl<'a> Iterator<u16> for Utf16CodeUnits<'a> {
         // every char gets either one u16 or two u16,
         // so this iterator is between 1 or 2 times as
         // long as the underlying iterator.
-        (low, high.and_then(|n| n.checked_mul(&2)))
+        (low, high.and_then(|n| n.checked_mul(2)))
     }
 }
 
diff --git a/src/libcoretest/num/int_macros.rs b/src/libcoretest/num/int_macros.rs
index 21b8f31dbf0..51af2e2916d 100644
--- a/src/libcoretest/num/int_macros.rs
+++ b/src/libcoretest/num/int_macros.rs
@@ -16,7 +16,6 @@ mod tests {
     use core::$T_i::*;
     use core::int;
     use num;
-    use core::num::CheckedDiv;
 
     #[test]
     fn test_overflows() {
@@ -152,9 +151,9 @@ mod tests {
 
     #[test]
     fn test_signed_checked_div() {
-        assert!(10i.checked_div(&2) == Some(5));
-        assert!(5i.checked_div(&0) == None);
-        assert!(int::MIN.checked_div(&-1) == None);
+        assert!(10i.checked_div(2) == Some(5));
+        assert!(5i.checked_div(0) == None);
+        assert!(int::MIN.checked_div(-1) == None);
     }
 }
 
diff --git a/src/libcoretest/num/uint_macros.rs b/src/libcoretest/num/uint_macros.rs
index e59e2378ba2..1d3f1718d72 100644
--- a/src/libcoretest/num/uint_macros.rs
+++ b/src/libcoretest/num/uint_macros.rs
@@ -15,7 +15,6 @@ macro_rules! uint_module (($T:ty, $T_i:ident) => (
 mod tests {
     use core::$T_i::*;
     use num;
-    use core::num::CheckedDiv;
 
     #[test]
     fn test_overflows() {
@@ -120,8 +119,8 @@ mod tests {
 
     #[test]
     fn test_unsigned_checked_div() {
-        assert!(10u.checked_div(&2) == Some(5));
-        assert!(5u.checked_div(&0) == None);
+        assert!(10u.checked_div(2) == Some(5));
+        assert!(5u.checked_div(0) == None);
     }
 }
 ))
diff --git a/src/librand/distributions/mod.rs b/src/librand/distributions/mod.rs
index 7d454e49006..26d5d3fb2f9 100644
--- a/src/librand/distributions/mod.rs
+++ b/src/librand/distributions/mod.rs
@@ -126,7 +126,7 @@ impl<'a, T: Clone> WeightedChoice<'a, T> {
         // weights so we can binary search. This *could* drop elements
         // with weight == 0 as an optimisation.
         for item in items.iter_mut() {
-            running_total = match running_total.checked_add(&item.weight) {
+            running_total = match running_total.checked_add(item.weight) {
                 Some(n) => n,
                 None => panic!("WeightedChoice::new called with a total weight \
                                larger than a uint can contain")
diff --git a/src/librustc/middle/trans/type_of.rs b/src/librustc/middle/trans/type_of.rs
index d1b8f767bc8..5e2df42d2d6 100644
--- a/src/librustc/middle/trans/type_of.rs
+++ b/src/librustc/middle/trans/type_of.rs
@@ -24,15 +24,13 @@ use middle::trans::type_::Type;
 use syntax::abi;
 use syntax::ast;
 
-use std::num::CheckedMul;
-
 // LLVM doesn't like objects that are too big. Issue #17913
 fn ensure_array_fits_in_address_space(ccx: &CrateContext,
                                       llet: Type,
                                       size: machine::llsize,
                                       scapegoat: ty::t) {
     let esz = machine::llsize_of_alloc(ccx, llet);
-    match esz.checked_mul(&size) {
+    match esz.checked_mul(size) {
         Some(n) if n < ccx.max_obj_size() => {}
         _ => { ccx.report_overbig_object(scapegoat) }
     }
diff --git a/src/librustc_back/sha2.rs b/src/librustc_back/sha2.rs
index 96a15213c5e..71d6ad791ec 100644
--- a/src/librustc_back/sha2.rs
+++ b/src/librustc_back/sha2.rs
@@ -61,14 +61,14 @@ impl ToBits for u64 {
 
 /// Adds the specified number of bytes to the bit count. panic!() if this would cause numeric
 /// overflow.
-fn add_bytes_to_bits<T: Int + CheckedAdd + ToBits>(bits: T, bytes: T) -> T {
+fn add_bytes_to_bits<T: Int + ToBits>(bits: T, bytes: T) -> T {
     let (new_high_bits, new_low_bits) = bytes.to_bits();
 
     if new_high_bits > Zero::zero() {
         panic!("numeric overflow occurred.")
     }
 
-    match bits.checked_add(&new_low_bits) {
+    match bits.checked_add(new_low_bits) {
         Some(x) => return x,
         None => panic!("numeric overflow occurred.")
     }
diff --git a/src/libserialize/json.rs b/src/libserialize/json.rs
index 77313517585..f387b660ed1 100644
--- a/src/libserialize/json.rs
+++ b/src/libserialize/json.rs
@@ -609,7 +609,7 @@ impl<'a> PrettyEncoder<'a> {
     /// This is safe to set during encoding.
     pub fn set_indent<'a>(&mut self, indent: uint) {
         // self.indent very well could be 0 so we need to use checked division.
-        let level = self.curr_indent.checked_div(&self.indent).unwrap_or(0);
+        let level = self.curr_indent.checked_div(self.indent).unwrap_or(0);
         self.indent = indent;
         self.curr_indent = level * self.indent;
     }
diff --git a/src/libstd/collections/hash/table.rs b/src/libstd/collections/hash/table.rs
index b39b15b3eb9..dd65a00d110 100644
--- a/src/libstd/collections/hash/table.rs
+++ b/src/libstd/collections/hash/table.rs
@@ -17,7 +17,7 @@ use iter::{Iterator, count};
 use kinds::{Sized, marker};
 use mem::{min_align_of, size_of};
 use mem;
-use num::{CheckedAdd, CheckedMul, UnsignedInt};
+use num::{Int, UnsignedInt};
 use ops::{Deref, DerefMut, Drop};
 use option::{Some, None, Option};
 use ptr::{RawPtr, copy_nonoverlapping_memory, zero_memory};
@@ -604,9 +604,9 @@ impl<K, V> RawTable<K, V> {
                 vals_size,   min_align_of::< V >());
 
         // One check for overflow that covers calculation and rounding of size.
-        let size_of_bucket = size_of::<u64>().checked_add(&size_of::<K>()).unwrap()
-                                             .checked_add(&size_of::<V>()).unwrap();
-        assert!(size >= capacity.checked_mul(&size_of_bucket)
+        let size_of_bucket = size_of::<u64>().checked_add(size_of::<K>()).unwrap()
+                                             .checked_add(size_of::<V>()).unwrap();
+        assert!(size >= capacity.checked_mul(size_of_bucket)
                                 .expect("capacity overflow"),
                 "capacity overflow");
 
diff --git a/src/libstd/num/mod.rs b/src/libstd/num/mod.rs
index fefde35ea21..2be88e01eed 100644
--- a/src/libstd/num/mod.rs
+++ b/src/libstd/num/mod.rs
@@ -24,7 +24,6 @@ pub use core::num::{Num, div_rem, Zero, zero, One, one};
 pub use core::num::{Signed, abs, signum};
 pub use core::num::{Unsigned, pow, Bounded};
 pub use core::num::{Primitive, Int, UnsignedInt};
-pub use core::num::{CheckedAdd, CheckedSub, CheckedMul, CheckedDiv};
 pub use core::num::{cast, FromPrimitive, NumCast, ToPrimitive};
 pub use core::num::{next_power_of_two, is_power_of_two};
 pub use core::num::{checked_next_power_of_two};
@@ -636,36 +635,36 @@ mod tests {
     #[test]
     fn test_checked_add() {
         let five_less = uint::MAX - 5;
-        assert_eq!(five_less.checked_add(&0), Some(uint::MAX - 5));
-        assert_eq!(five_less.checked_add(&1), Some(uint::MAX - 4));
-        assert_eq!(five_less.checked_add(&2), Some(uint::MAX - 3));
-        assert_eq!(five_less.checked_add(&3), Some(uint::MAX - 2));
-        assert_eq!(five_less.checked_add(&4), Some(uint::MAX - 1));
-        assert_eq!(five_less.checked_add(&5), Some(uint::MAX));
-        assert_eq!(five_less.checked_add(&6), None);
-        assert_eq!(five_less.checked_add(&7), None);
+        assert_eq!(five_less.checked_add(0), Some(uint::MAX - 5));
+        assert_eq!(five_less.checked_add(1), Some(uint::MAX - 4));
+        assert_eq!(five_less.checked_add(2), Some(uint::MAX - 3));
+        assert_eq!(five_less.checked_add(3), Some(uint::MAX - 2));
+        assert_eq!(five_less.checked_add(4), Some(uint::MAX - 1));
+        assert_eq!(five_less.checked_add(5), Some(uint::MAX));
+        assert_eq!(five_less.checked_add(6), None);
+        assert_eq!(five_less.checked_add(7), None);
     }
 
     #[test]
     fn test_checked_sub() {
-        assert_eq!(5u.checked_sub(&0), Some(5));
-        assert_eq!(5u.checked_sub(&1), Some(4));
-        assert_eq!(5u.checked_sub(&2), Some(3));
-        assert_eq!(5u.checked_sub(&3), Some(2));
-        assert_eq!(5u.checked_sub(&4), Some(1));
-        assert_eq!(5u.checked_sub(&5), Some(0));
-        assert_eq!(5u.checked_sub(&6), None);
-        assert_eq!(5u.checked_sub(&7), None);
+        assert_eq!(5u.checked_sub(0), Some(5));
+        assert_eq!(5u.checked_sub(1), Some(4));
+        assert_eq!(5u.checked_sub(2), Some(3));
+        assert_eq!(5u.checked_sub(3), Some(2));
+        assert_eq!(5u.checked_sub(4), Some(1));
+        assert_eq!(5u.checked_sub(5), Some(0));
+        assert_eq!(5u.checked_sub(6), None);
+        assert_eq!(5u.checked_sub(7), None);
     }
 
     #[test]
     fn test_checked_mul() {
         let third = uint::MAX / 3;
-        assert_eq!(third.checked_mul(&0), Some(0));
-        assert_eq!(third.checked_mul(&1), Some(third));
-        assert_eq!(third.checked_mul(&2), Some(third * 2));
-        assert_eq!(third.checked_mul(&3), Some(third * 3));
-        assert_eq!(third.checked_mul(&4), None);
+        assert_eq!(third.checked_mul(0), Some(0));
+        assert_eq!(third.checked_mul(1), Some(third));
+        assert_eq!(third.checked_mul(2), Some(third * 2));
+        assert_eq!(third.checked_mul(3), Some(third * 3));
+        assert_eq!(third.checked_mul(4), None);
     }
 
     macro_rules! test_next_power_of_two(
diff --git a/src/libstd/num/strconv.rs b/src/libstd/num/strconv.rs
index 088ea89818e..875d03d6c25 100644
--- a/src/libstd/num/strconv.rs
+++ b/src/libstd/num/strconv.rs
@@ -601,11 +601,11 @@ pub fn from_str_radix_int<T: Int>(src: &str, radix: uint) -> Option<T> {
                 Some(x) => x,
                 None => return None,
             };
-            result = match result.checked_mul(&radix) {
+            result = match result.checked_mul(radix) {
                 Some(result) => result,
                 None => return None,
             };
-            result = match result.checked_add(&x) {
+            result = match result.checked_add(x) {
                 Some(result) => result,
                 None => return None,
             };
@@ -616,11 +616,11 @@ pub fn from_str_radix_int<T: Int>(src: &str, radix: uint) -> Option<T> {
                 Some(x) => x,
                 None => return None,
             };
-            result = match result.checked_mul(&radix) {
+            result = match result.checked_mul(radix) {
                 Some(result) => result,
                 None => return None,
             };
-            result = match result.checked_sub(&x) {
+            result = match result.checked_sub(x) {
                 Some(result) => result,
                 None => return None,
             };
diff --git a/src/libstd/prelude.rs b/src/libstd/prelude.rs
index f1090e75127..3c20d205b77 100644
--- a/src/libstd/prelude.rs
+++ b/src/libstd/prelude.rs
@@ -67,7 +67,7 @@
 #[doc(no_inline)] pub use iter::{Iterator, DoubleEndedIterator};
 #[doc(no_inline)] pub use iter::{RandomAccessIterator, CloneableIterator};
 #[doc(no_inline)] pub use iter::{OrdIterator, MutableDoubleEndedIterator};
-#[doc(no_inline)] pub use num::{Num, NumCast, CheckedAdd, CheckedSub, CheckedMul, CheckedDiv};
+#[doc(no_inline)] pub use num::{Num, NumCast};
 #[doc(no_inline)] pub use num::{Signed, Unsigned, Primitive, Int, Float};
 #[doc(no_inline)] pub use num::{FloatMath, ToPrimitive, FromPrimitive};
 #[doc(no_inline)] pub use boxed::Box;
diff --git a/src/libstd/time/duration.rs b/src/libstd/time/duration.rs
index c3adae8cff8..6afeb76b83f 100644
--- a/src/libstd/time/duration.rs
+++ b/src/libstd/time/duration.rs
@@ -15,8 +15,7 @@
 use {fmt, i64};
 use ops::{Add, Sub, Mul, Div, Neg};
 use option::{Option, Some, None};
-use num;
-use num::{CheckedAdd, CheckedMul};
+use num::Int;
 use result::{Result, Ok, Err};
 
 /// The number of nanoseconds in a microsecond.
@@ -69,7 +68,7 @@ impl Duration {
     /// Fails when the duration is out of bounds.
     #[inline]
     pub fn weeks(weeks: i64) -> Duration {
-        let secs = weeks.checked_mul(&SECS_PER_WEEK).expect("Duration::weeks out of bounds");
+        let secs = weeks.checked_mul(SECS_PER_WEEK).expect("Duration::weeks out of bounds");
         Duration::seconds(secs)
     }
 
@@ -78,7 +77,7 @@ impl Duration {
     /// Fails when the duration is out of bounds.
     #[inline]
     pub fn days(days: i64) -> Duration {
-        let secs = days.checked_mul(&SECS_PER_DAY).expect("Duration::days out of bounds");
+        let secs = days.checked_mul(SECS_PER_DAY).expect("Duration::days out of bounds");
         Duration::seconds(secs)
     }
 
@@ -87,7 +86,7 @@ impl Duration {
     /// Fails when the duration is out of bounds.
     #[inline]
     pub fn hours(hours: i64) -> Duration {
-        let secs = hours.checked_mul(&SECS_PER_HOUR).expect("Duration::hours ouf of bounds");
+        let secs = hours.checked_mul(SECS_PER_HOUR).expect("Duration::hours ouf of bounds");
         Duration::seconds(secs)
     }
 
@@ -96,7 +95,7 @@ impl Duration {
     /// Fails when the duration is out of bounds.
     #[inline]
     pub fn minutes(minutes: i64) -> Duration {
-        let secs = minutes.checked_mul(&SECS_PER_MINUTE).expect("Duration::minutes out of bounds");
+        let secs = minutes.checked_mul(SECS_PER_MINUTE).expect("Duration::minutes out of bounds");
         Duration::seconds(secs)
     }
 
@@ -191,33 +190,64 @@ impl Duration {
     /// Returns the total number of whole microseconds in the duration,
     /// or `None` on overflow (exceeding 2^63 microseconds in either direction).
     pub fn num_microseconds(&self) -> Option<i64> {
-        let secs_part = try_opt!(self.num_seconds().checked_mul(&MICROS_PER_SEC));
+        let secs_part = try_opt!(self.num_seconds().checked_mul(MICROS_PER_SEC));
         let nanos_part = self.nanos_mod_sec() / NANOS_PER_MICRO;
-        secs_part.checked_add(&(nanos_part as i64))
+        secs_part.checked_add(nanos_part as i64)
     }
 
     /// Returns the total number of whole nanoseconds in the duration,
     /// or `None` on overflow (exceeding 2^63 nanoseconds in either direction).
     pub fn num_nanoseconds(&self) -> Option<i64> {
-        let secs_part = try_opt!(self.num_seconds().checked_mul(&(NANOS_PER_SEC as i64)));
+        let secs_part = try_opt!(self.num_seconds().checked_mul(NANOS_PER_SEC as i64));
         let nanos_part = self.nanos_mod_sec();
-        secs_part.checked_add(&(nanos_part as i64))
+        secs_part.checked_add(nanos_part as i64)
     }
-}
 
-impl num::Bounded for Duration {
-    #[inline] fn min_value() -> Duration { MIN }
-    #[inline] fn max_value() -> Duration { MAX }
-}
+    /// Add two durations, returning `None` if overflow occured.
+    pub fn checked_add(&self, rhs: &Duration) -> Option<Duration> {
+        let mut secs = try_opt!(self.secs.checked_add(rhs.secs));
+        let mut nanos = self.nanos + rhs.nanos;
+        if nanos >= NANOS_PER_SEC {
+            nanos -= NANOS_PER_SEC;
+            secs = try_opt!(secs.checked_add(1));
+        }
+        let d = Duration { secs: secs, nanos: nanos };
+        // Even if d is within the bounds of i64 seconds,
+        // it might still overflow i64 milliseconds.
+        if d < MIN || d > MAX { None } else { Some(d) }
+    }
+
+    /// Subtract two durations, returning `None` if overflow occured.
+    pub fn checked_sub(&self, rhs: &Duration) -> Option<Duration> {
+        let mut secs = try_opt!(self.secs.checked_sub(rhs.secs));
+        let mut nanos = self.nanos - rhs.nanos;
+        if nanos < 0 {
+            nanos += NANOS_PER_SEC;
+            secs = try_opt!(secs.checked_sub(1));
+        }
+        let d = Duration { secs: secs, nanos: nanos };
+        // Even if d is within the bounds of i64 seconds,
+        // it might still overflow i64 milliseconds.
+        if d < MIN || d > MAX { None } else { Some(d) }
+    }
 
-impl num::Zero for Duration {
+    /// The minimum possible `Duration`: `i64::MIN` milliseconds.
     #[inline]
-    fn zero() -> Duration {
+    pub fn min_value() -> Duration { MIN }
+
+    /// The maximum possible `Duration`: `i64::MAX` milliseconds.
+    #[inline]
+    pub fn max_value() -> Duration { MAX }
+
+    /// A duration where the stored seconds and nanoseconds are equal to zero.
+    #[inline]
+    pub fn zero() -> Duration {
         Duration { secs: 0, nanos: 0 }
     }
 
+    /// Returns `true` if the duration equals `Duration::zero()`.
     #[inline]
-    fn is_zero(&self) -> bool {
+    pub fn is_zero(&self) -> bool {
         self.secs == 0 && self.nanos == 0
     }
 }
@@ -245,21 +275,6 @@ impl Add<Duration,Duration> for Duration {
     }
 }
 
-impl num::CheckedAdd for Duration {
-    fn checked_add(&self, rhs: &Duration) -> Option<Duration> {
-        let mut secs = try_opt!(self.secs.checked_add(&rhs.secs));
-        let mut nanos = self.nanos + rhs.nanos;
-        if nanos >= NANOS_PER_SEC {
-            nanos -= NANOS_PER_SEC;
-            secs = try_opt!(secs.checked_add(&1));
-        }
-        let d = Duration { secs: secs, nanos: nanos };
-        // Even if d is within the bounds of i64 seconds,
-        // it might still overflow i64 milliseconds.
-        if d < MIN || d > MAX { None } else { Some(d) }
-    }
-}
-
 impl Sub<Duration,Duration> for Duration {
     fn sub(&self, rhs: &Duration) -> Duration {
         let mut secs = self.secs - rhs.secs;
@@ -272,21 +287,6 @@ impl Sub<Duration,Duration> for Duration {
     }
 }
 
-impl num::CheckedSub for Duration {
-    fn checked_sub(&self, rhs: &Duration) -> Option<Duration> {
-        let mut secs = try_opt!(self.secs.checked_sub(&rhs.secs));
-        let mut nanos = self.nanos - rhs.nanos;
-        if nanos < 0 {
-            nanos += NANOS_PER_SEC;
-            secs = try_opt!(secs.checked_sub(&1));
-        }
-        let d = Duration { secs: secs, nanos: nanos };
-        // Even if d is within the bounds of i64 seconds,
-        // it might still overflow i64 milliseconds.
-        if d < MIN || d > MAX { None } else { Some(d) }
-    }
-}
-
 impl Mul<i32,Duration> for Duration {
     fn mul(&self, rhs: &i32) -> Duration {
         // Multiply nanoseconds as i64, because it cannot overflow that way.
@@ -379,15 +379,12 @@ fn div_rem_64(this: i64, other: i64) -> (i64, i64) {
 mod tests {
     use super::{Duration, MIN, MAX};
     use {i32, i64};
-    use num::{Zero, CheckedAdd, CheckedSub};
     use option::{Some, None};
     use to_string::ToString;
 
     #[test]
     fn test_duration() {
-        let d: Duration = Zero::zero();
-        assert_eq!(d, Zero::zero());
-        assert!(Duration::seconds(1) != Zero::zero());
+        assert!(Duration::seconds(1) != Duration::zero());
         assert_eq!(Duration::seconds(1) + Duration::seconds(2), Duration::seconds(3));
         assert_eq!(Duration::seconds(86399) + Duration::seconds(4),
                    Duration::days(1) + Duration::seconds(3));
@@ -403,8 +400,7 @@ mod tests {
 
     #[test]
     fn test_duration_num_days() {
-        let d: Duration = Zero::zero();
-        assert_eq!(d.num_days(), 0);
+        assert_eq!(Duration::zero().num_days(), 0);
         assert_eq!(Duration::days(1).num_days(), 1);
         assert_eq!(Duration::days(-1).num_days(), -1);
         assert_eq!(Duration::seconds(86399).num_days(), 0);
@@ -417,8 +413,7 @@ mod tests {
 
     #[test]
     fn test_duration_num_seconds() {
-        let d: Duration = Zero::zero();
-        assert_eq!(d.num_seconds(), 0);
+        assert_eq!(Duration::zero().num_seconds(), 0);
         assert_eq!(Duration::seconds(1).num_seconds(), 1);
         assert_eq!(Duration::seconds(-1).num_seconds(), -1);
         assert_eq!(Duration::milliseconds(999).num_seconds(), 0);
@@ -429,8 +424,7 @@ mod tests {
 
     #[test]
     fn test_duration_num_milliseconds() {
-        let d: Duration = Zero::zero();
-        assert_eq!(d.num_milliseconds(), 0);
+        assert_eq!(Duration::zero().num_milliseconds(), 0);
         assert_eq!(Duration::milliseconds(1).num_milliseconds(), 1);
         assert_eq!(Duration::milliseconds(-1).num_milliseconds(), -1);
         assert_eq!(Duration::microseconds(999).num_milliseconds(), 0);
@@ -445,8 +439,7 @@ mod tests {
 
     #[test]
     fn test_duration_num_microseconds() {
-        let d: Duration = Zero::zero();
-        assert_eq!(d.num_microseconds(), Some(0));
+        assert_eq!(Duration::zero().num_microseconds(), Some(0));
         assert_eq!(Duration::microseconds(1).num_microseconds(), Some(1));
         assert_eq!(Duration::microseconds(-1).num_microseconds(), Some(-1));
         assert_eq!(Duration::nanoseconds(999).num_microseconds(), Some(0));
@@ -470,8 +463,7 @@ mod tests {
 
     #[test]
     fn test_duration_num_nanoseconds() {
-        let d: Duration = Zero::zero();
-        assert_eq!(d.num_nanoseconds(), Some(0));
+        assert_eq!(Duration::zero().num_nanoseconds(), Some(0));
         assert_eq!(Duration::nanoseconds(1).num_nanoseconds(), Some(1));
         assert_eq!(Duration::nanoseconds(-1).num_nanoseconds(), Some(-1));
         assert_eq!(Duration::nanoseconds(i64::MAX).num_nanoseconds(), Some(i64::MAX));
@@ -504,10 +496,9 @@ mod tests {
 
     #[test]
     fn test_duration_mul() {
-        let d: Duration = Zero::zero();
-        assert_eq!(d * i32::MAX, d);
-        assert_eq!(d * i32::MIN, d);
-        assert_eq!(Duration::nanoseconds(1) * 0, Zero::zero());
+        assert_eq!(Duration::zero() * i32::MAX, Duration::zero());
+        assert_eq!(Duration::zero() * i32::MIN, Duration::zero());
+        assert_eq!(Duration::nanoseconds(1) * 0, Duration::zero());
         assert_eq!(Duration::nanoseconds(1) * 1, Duration::nanoseconds(1));
         assert_eq!(Duration::nanoseconds(1) * 1_000_000_000, Duration::seconds(1));
         assert_eq!(Duration::nanoseconds(1) * -1_000_000_000, -Duration::seconds(1));
@@ -522,9 +513,8 @@ mod tests {
 
     #[test]
     fn test_duration_div() {
-        let d: Duration = Zero::zero();
-        assert_eq!(d / i32::MAX, d);
-        assert_eq!(d / i32::MIN, d);
+        assert_eq!(Duration::zero() / i32::MAX, Duration::zero());
+        assert_eq!(Duration::zero() / i32::MIN, Duration::zero());
         assert_eq!(Duration::nanoseconds(123_456_789) / 1, Duration::nanoseconds(123_456_789));
         assert_eq!(Duration::nanoseconds(123_456_789) / -1, -Duration::nanoseconds(123_456_789));
         assert_eq!(-Duration::nanoseconds(123_456_789) / -1, Duration::nanoseconds(123_456_789));
@@ -540,8 +530,7 @@ mod tests {
 
     #[test]
     fn test_duration_fmt() {
-        let d: Duration = Zero::zero();
-        assert_eq!(d.to_string(), "PT0S".to_string());
+        assert_eq!(Duration::zero().to_string(), "PT0S".to_string());
         assert_eq!(Duration::days(42).to_string(), "P42D".to_string());
         assert_eq!(Duration::days(-42).to_string(), "-P42D".to_string());
         assert_eq!(Duration::seconds(42).to_string(), "PT42S".to_string());
diff --git a/src/libsyntax/parse/mod.rs b/src/libsyntax/parse/mod.rs
index 996708b2174..0f364d1ba0b 100644
--- a/src/libsyntax/parse/mod.rs
+++ b/src/libsyntax/parse/mod.rs
@@ -63,7 +63,7 @@ impl ParseSess {
     pub fn reserve_node_ids(&self, count: ast::NodeId) -> ast::NodeId {
         let v = self.node_id.get();
 
-        match v.checked_add(&count) {
+        match v.checked_add(count) {
             Some(next) => { self.node_id.set(next); }
             None => panic!("Input too large, ran out of node ids!")
         }