Use associated constants in std::num::{Zero,One}

This commit causes an ICE!

src/libcore/fmt/num.rs

@@ -52,7 +52,7 @@ trait GenericRadix {
     fn fmt_int<T: Int>(&self, mut x: T, f: &mut fmt::Formatter) -> fmt::Result {
         // The radix can be as low as 2, so we need a buffer of at least 64
         // characters for a base 2 number.
-        let zero = T::zero();
+        let zero = T::ZERO;
         let is_positive = x >= zero;
         let mut buf = [0; 64];
         let mut curr = buf.len();

src/libcore/iter.rs

@@ -1075,7 +1075,7 @@ pub trait Iterator {
         S: Add<Self::Item, Output=S> + Zero,
         Self: Sized,
     {
-        self.fold(Zero::zero(), |s, e| s + e)
+        self.fold(Zero::ZERO, |s, e| s + e)
     }
 
     /// Iterates over the entire iterator, multiplying all the elements
@@ -1097,7 +1097,7 @@ pub trait Iterator {
         P: Mul<Self::Item, Output=P> + One,
         Self: Sized,
     {
-        self.fold(One::one(), |p, e| p * e)
+        self.fold(One::ONE, |p, e| p * e)
     }
 }
 
@@ -2840,7 +2840,7 @@ impl<A> DoubleEndedIterator for RangeInclusive<A> where
     fn next_back(&mut self) -> Option<A> {
         if self.range.end > self.range.start {
             let result = self.range.end.clone();
-            self.range.end = &self.range.end - &A::one();
+            self.range.end = &self.range.end - &A::ONE;
             Some(result)
         } else if !self.done && self.range.start == self.range.end {
             self.done = true;
@@ -2858,7 +2858,7 @@ impl<A: Step + Zero + Clone> Iterator for StepBy<A, ops::Range<A>> {
 
     #[inline]
     fn next(&mut self) -> Option<A> {
-        let rev = self.step_by < A::zero();
+        let rev = self.step_by < A::ZERO;
         if (rev && self.range.start > self.range.end) ||
            (!rev && self.range.start < self.range.end)
         {
@@ -2906,7 +2906,7 @@ impl<A: Step + One> Iterator for ops::Range<A> where
     #[inline]
     fn next(&mut self) -> Option<A> {
         if self.start < self.end {
-            let mut n = &self.start + &A::one();
+            let mut n = &self.start + &A::ONE;
             mem::swap(&mut n, &mut self.start);
             Some(n)
         } else {
@@ -2916,7 +2916,7 @@ impl<A: Step + One> Iterator for ops::Range<A> where
 
     #[inline]
     fn size_hint(&self) -> (usize, Option<usize>) {
-        match Step::steps_between(&self.start, &self.end, &A::one()) {
+        match Step::steps_between(&self.start, &self.end, &A::ONE) {
             Some(hint) => (hint, Some(hint)),
             None => (0, None)
         }
@@ -2936,7 +2936,7 @@ impl<A: Step + One + Clone> DoubleEndedIterator for ops::Range<A> where
     #[inline]
     fn next_back(&mut self) -> Option<A> {
         if self.start < self.end {
-            self.end = &self.end - &A::one();
+            self.end = &self.end - &A::ONE;
             Some(self.end.clone())
         } else {
             None
@@ -2953,7 +2953,7 @@ impl<A: Step + One> Iterator for ops::RangeFrom<A> where
 
     #[inline]
     fn next(&mut self) -> Option<A> {
-        let mut n = &self.start + &A::one();
+        let mut n = &self.start + &A::ONE;
         mem::swap(&mut n, &mut self.start);
         Some(n)
     }

src/libcore/lib.rs

@@ -67,6 +67,7 @@
 #![feature(on_unimplemented)]
 #![feature(simd)]
 #![feature(staged_api)]
+#![feature(associated_consts)]
 #![feature(unboxed_closures)]
 #![feature(rustc_attrs)]
 #![feature(optin_builtin_traits)]

src/libcore/num/mod.rs

@@ -50,34 +50,30 @@ pub mod flt2dec;
 /// Types that have a "zero" value.
 ///
 /// This trait is intended for use in conjunction with `Add`, as an identity:
-/// `x + T::zero() == x`.
-#[unstable(feature = "zero_one",
-           reason = "unsure of placement, wants to use associated constants")]
+/// `x + T::ZERO == x`.
+#[unstable(feature = "zero_one", reason = "unsure of placement")]
 pub trait Zero {
     /// The "zero" (usually, additive identity) for this type.
-    fn zero() -> Self;
+    const ZERO: Self;
 }
 
 /// Types that have a "one" value.
 ///
 /// This trait is intended for use in conjunction with `Mul`, as an identity:
-/// `x * T::one() == x`.
-#[unstable(feature = "zero_one",
-           reason = "unsure of placement, wants to use associated constants")]
+/// `x * T::ONE == x`.
+#[unstable(feature = "zero_one", reason = "unsure of placement")]
 pub trait One {
     /// The "one" (usually, multiplicative identity) for this type.
-    fn one() -> Self;
+    const ONE: Self;
 }
 
 macro_rules! zero_one_impl {
     ($($t:ty)*) => ($(
         impl Zero for $t {
-            #[inline]
-            fn zero() -> Self { 0 }
+            const ZERO: $t = 0;
         }
         impl One for $t {
-            #[inline]
-            fn one() -> Self { 1 }
+            const ONE: $t = 1;
         }
     )*)
 }
@@ -86,12 +82,10 @@ zero_one_impl! { u8 u16 u32 u64 usize i8 i16 i32 i64 isize }
 macro_rules! zero_one_impl_float {
     ($($t:ty)*) => ($(
         impl Zero for $t {
-            #[inline]
-            fn zero() -> Self { 0.0 }
+            const ZERO: $t = 0.0;
         }
         impl One for $t {
-            #[inline]
-            fn one() -> Self { 1.0 }
+            const ONE: $t = 1.0;
         }
     )*)
 }
@@ -415,7 +409,7 @@ macro_rules! int_impl {
         pub fn saturating_add(self, other: Self) -> Self {
             match self.checked_add(other) {
                 Some(x)                       => x,
-                None if other >= Self::zero() => Self::max_value(),
+                None if other >= Self::ZERO => Self::max_value(),
                 None => Self::min_value(),
             }
         }
@@ -427,7 +421,7 @@ macro_rules! int_impl {
         pub fn saturating_sub(self, other: Self) -> Self {
             match self.checked_sub(other) {
                 Some(x)                      => x,
-                None if other >= Self::zero() => Self::min_value(),
+                None if other >= Self::ZERO => Self::min_value(),
                 None => Self::max_value(),
             }
         }
@@ -535,7 +529,7 @@ macro_rules! int_impl {
         #[inline]
         pub fn pow(self, mut exp: u32) -> Self {
             let mut base = self;
-            let mut acc = Self::one();
+            let mut acc = Self::ONE;
 
             let mut prev_base = self;
             let mut base_oflo = false;
@@ -985,7 +979,7 @@ macro_rules! uint_impl {
         pub fn saturating_add(self, other: Self) -> Self {
             match self.checked_add(other) {
                 Some(x)                       => x,
-                None if other >= Self::zero() => Self::max_value(),
+                None if other >= Self::ZERO => Self::max_value(),
                 None => Self::min_value(),
             }
         }
@@ -997,7 +991,7 @@ macro_rules! uint_impl {
         pub fn saturating_sub(self, other: Self) -> Self {
             match self.checked_sub(other) {
                 Some(x)                       => x,
-                None if other >= Self::zero() => Self::min_value(),
+                None if other >= Self::ZERO => Self::min_value(),
                 None => Self::max_value(),
             }
         }
@@ -1103,7 +1097,7 @@ macro_rules! uint_impl {
         #[inline]
         pub fn pow(self, mut exp: u32) -> Self {
             let mut base = self;
-            let mut acc = Self::one();
+            let mut acc = Self::ONE;
 
             let mut prev_base = self;
             let mut base_oflo = false;
@@ -1131,8 +1125,8 @@ macro_rules! uint_impl {
         #[stable(feature = "rust1", since = "1.0.0")]
         #[inline]
         pub fn is_power_of_two(self) -> bool {
-            (self.wrapping_sub(Self::one())) & self == Self::zero() &&
-                !(self == Self::zero())
+            (self.wrapping_sub(Self::ONE)) & self == Self::ZERO &&
+                !(self == Self::ZERO)
         }
 
         /// Returns the smallest power of two greater than or equal to `self`.
@@ -1141,7 +1135,7 @@ macro_rules! uint_impl {
         #[inline]
         pub fn next_power_of_two(self) -> Self {
             let bits = size_of::<Self>() * 8;
-            let one: Self = Self::one();
+            let one = Self::ONE;
             one << ((bits - self.wrapping_sub(one).leading_zeros() as usize) % bits)
         }
 

src/libstd/num/mod.rs

@@ -202,7 +202,7 @@ mod tests {
     #[test]
     fn test_pow() {
         fn naive_pow<T: Mul<Output=T> + One + Copy>(base: T, exp: usize) -> T {
-            let one: T = T::one();
+            let one: T = T::ONE;
             (0..exp).fold(one, |acc, _| acc * base)
         }
         macro_rules! assert_pow {

src/libstd/sys/unix/mod.rs

@@ -75,7 +75,7 @@ pub fn decode_error_kind(errno: i32) -> ErrorKind {
 }
 
 pub fn cvt<T: One + PartialEq + Neg<Output=T>>(t: T) -> io::Result<T> {
-    let one: T = T::one();
+    let one: T = T::ONE;
     if t == -one {
         Err(io::Error::last_os_error())
     } else {

src/libstd/sys/windows/mod.rs

@@ -145,7 +145,7 @@ pub fn truncate_utf16_at_nul<'a>(v: &'a [u16]) -> &'a [u16] {
 }
 
 fn cvt<I: PartialEq + Zero>(i: I) -> io::Result<I> {
-    if i == I::zero() {
+    if i == I::ZERO {
         Err(io::Error::last_os_error())
     } else {
         Ok(i)

src/libstd/sys/windows/net.rs

@@ -50,7 +50,7 @@ fn last_error() -> io::Error {
 /// and if so, returns the last error from the Windows socket interface. . This
 /// function must be called before another call to the socket API is made.
 pub fn cvt<T: One + Neg<Output=T> + PartialEq>(t: T) -> io::Result<T> {
-    let one: T = T::one();
+    let one: T = T::ONE;
     if t == -one {
         Err(last_error())
     } else {

src/test/run-pass/issue-8460.rs

@@ -19,19 +19,19 @@ fn main() {
     assert!(thread::spawn(move|| { i16::min_value() / -1; }).join().is_err());
     assert!(thread::spawn(move|| { i32::min_value() / -1; }).join().is_err());
     assert!(thread::spawn(move|| { i64::min_value() / -1; }).join().is_err());
-    assert!(thread::spawn(move|| { 1isize / isize::zero(); }).join().is_err());
-    assert!(thread::spawn(move|| { 1i8 / i8::zero(); }).join().is_err());
-    assert!(thread::spawn(move|| { 1i16 / i16::zero(); }).join().is_err());
-    assert!(thread::spawn(move|| { 1i32 / i32::zero(); }).join().is_err());
-    assert!(thread::spawn(move|| { 1i64 / i64::zero(); }).join().is_err());
+    assert!(thread::spawn(move|| { 1isize / isize::ZERO; }).join().is_err());
+    assert!(thread::spawn(move|| { 1i8 / i8::ZERO; }).join().is_err());
+    assert!(thread::spawn(move|| { 1i16 / i16::ZERO; }).join().is_err());
+    assert!(thread::spawn(move|| { 1i32 / i32::ZERO; }).join().is_err());
+    assert!(thread::spawn(move|| { 1i64 / i64::ZERO; }).join().is_err());
     assert!(thread::spawn(move|| { isize::min_value() % -1; }).join().is_err());
     assert!(thread::spawn(move|| { i8::min_value() % -1; }).join().is_err());
     assert!(thread::spawn(move|| { i16::min_value() % -1; }).join().is_err());
     assert!(thread::spawn(move|| { i32::min_value() % -1; }).join().is_err());
     assert!(thread::spawn(move|| { i64::min_value() % -1; }).join().is_err());
-    assert!(thread::spawn(move|| { 1isize % isize::zero(); }).join().is_err());
-    assert!(thread::spawn(move|| { 1i8 % i8::zero(); }).join().is_err());
-    assert!(thread::spawn(move|| { 1i16 % i16::zero(); }).join().is_err());
-    assert!(thread::spawn(move|| { 1i32 % i32::zero(); }).join().is_err());
-    assert!(thread::spawn(move|| { 1i64 % i64::zero(); }).join().is_err());
+    assert!(thread::spawn(move|| { 1isize % isize::ZERO; }).join().is_err());
+    assert!(thread::spawn(move|| { 1i8 % i8::ZERO; }).join().is_err());
+    assert!(thread::spawn(move|| { 1i16 % i16::ZERO; }).join().is_err());
+    assert!(thread::spawn(move|| { 1i32 % i32::ZERO; }).join().is_err());
+    assert!(thread::spawn(move|| { 1i64 % i64::ZERO; }).join().is_err());
 }