rollup merge of #23945: pnkfelix/gate-u-negate

Feature-gate  unsigned unary negate.

Discussed in weekly meeting here: https://github.com/rust-lang/meeting-minutes/blob/master/weekly-meetings/2015-03-31.md#feature-gate--expr

and also in the internals thread here: http://internals.rust-lang.org/t/forbid-unsigned-integer/752

src/libcore/atomic.rs

@@ -161,7 +161,7 @@ pub const ATOMIC_USIZE_INIT: AtomicUsize =
         AtomicUsize { v: UnsafeCell { value: 0, } };
 
 // NB: Needs to be -1 (0b11111111...) to make fetch_nand work correctly
-const UINT_TRUE: usize = -1;
+const UINT_TRUE: usize = !0;
 
 impl AtomicBool {
     /// Creates a new `AtomicBool`.

src/libcore/cell.rs

@@ -287,7 +287,7 @@ pub enum BorrowState {
 // (will not outgrow its range since `usize` is the size of the address space)
 type BorrowFlag = usize;
 const UNUSED: BorrowFlag = 0;
-const WRITING: BorrowFlag = -1;
+const WRITING: BorrowFlag = !0;
 
 impl<T> RefCell<T> {
     /// Creates a new `RefCell` containing `value`.

src/libcore/num/mod.rs

@@ -516,7 +516,7 @@ macro_rules! uint_impl {
             fn min_value() -> $T { 0 }
 
             #[inline]
-            fn max_value() -> $T { -1 }
+            fn max_value() -> $T { !0 }
 
             #[inline]
             fn count_ones(self) -> u32 {

src/libcore/num/wrapping.rs

@@ -30,7 +30,7 @@ use intrinsics::{i16_mul_with_overflow, u16_mul_with_overflow};
 use intrinsics::{i32_mul_with_overflow, u32_mul_with_overflow};
 use intrinsics::{i64_mul_with_overflow, u64_mul_with_overflow};
 
-use ::{i8,i16,i32,i64,u8,u16,u32,u64};
+use ::{i8,i16,i32,i64};
 
 #[unstable(feature = "core", reason = "may be removed, renamed, or relocated")]
 #[deprecated(since = "1.0.0", reason = "moved to inherent methods")]
@@ -206,7 +206,7 @@ mod shift_max {
     pub const u64: u32 = i64;
 }
 
-macro_rules! overflowing_impl {
+macro_rules! signed_overflowing_impl {
     ($($t:ident)*) => ($(
         impl OverflowingOps for $t {
             #[inline(always)]
@@ -259,7 +259,53 @@ macro_rules! overflowing_impl {
     )*)
 }
 
-overflowing_impl! { u8 u16 u32 u64 i8 i16 i32 i64 }
+macro_rules! unsigned_overflowing_impl {
+    ($($t:ident)*) => ($(
+        impl OverflowingOps for $t {
+            #[inline(always)]
+            fn overflowing_add(self, rhs: $t) -> ($t, bool) {
+                unsafe {
+                    concat_idents!($t, _add_with_overflow)(self, rhs)
+                }
+            }
+            #[inline(always)]
+            fn overflowing_sub(self, rhs: $t) -> ($t, bool) {
+                unsafe {
+                    concat_idents!($t, _sub_with_overflow)(self, rhs)
+                }
+            }
+            #[inline(always)]
+            fn overflowing_mul(self, rhs: $t) -> ($t, bool) {
+                unsafe {
+                    concat_idents!($t, _mul_with_overflow)(self, rhs)
+                }
+            }
+
+            #[inline(always)]
+            fn overflowing_div(self, rhs: $t) -> ($t, bool) {
+                (self/rhs, false)
+            }
+            #[inline(always)]
+            fn overflowing_rem(self, rhs: $t) -> ($t, bool) {
+                (self % rhs, false)
+            }
+
+            #[inline(always)]
+            fn overflowing_shl(self, rhs: u32) -> ($t, bool) {
+                (self << (rhs & self::shift_max::$t),
+                 (rhs > self::shift_max::$t))
+            }
+            #[inline(always)]
+            fn overflowing_shr(self, rhs: u32) -> ($t, bool) {
+                (self >> (rhs & self::shift_max::$t),
+                 (rhs > self::shift_max::$t))
+            }
+        }
+    )*)
+}
+
+signed_overflowing_impl! { i8 i16 i32 i64 }
+unsigned_overflowing_impl! { u8 u16 u32 u64 }
 
 #[cfg(target_pointer_width = "64")]
 impl OverflowingOps for usize {

src/libcore/ops.rs

@@ -482,8 +482,10 @@ pub trait Neg {
     fn neg(self) -> Self::Output;
 }
 
-macro_rules! neg_impl {
-    ($($t:ty)*) => ($(
+
+
+macro_rules! neg_impl_core {
+    ($id:ident => $body:expr, $($t:ty)*) => ($(
         #[stable(feature = "rust1", since = "1.0.0")]
         #[allow(unsigned_negation)]
         impl Neg for $t {
@@ -492,14 +494,28 @@ macro_rules! neg_impl {
 
             #[inline]
             #[stable(feature = "rust1", since = "1.0.0")]
-            fn neg(self) -> $t { -self }
+            fn neg(self) -> $t { let $id = self; $body }
         }
 
         forward_ref_unop! { impl Neg, neg for $t }
     )*)
 }
 
-neg_impl! { usize u8 u16 u32 u64 isize i8 i16 i32 i64 f32 f64 }
+macro_rules! neg_impl_numeric {
+    ($($t:ty)*) => { neg_impl_core!{ x => -x, $($t)*} }
+}
+
+macro_rules! neg_impl_unsigned {
+    ($($t:ty)*) => {
+        neg_impl_core!{ x => {
+            #[cfg(stage0)]
+            use ::num::wrapping::WrappingOps;
+            !x.wrapping_add(1)
+        }, $($t)*} }
+}
+
+// neg_impl_unsigned! { usize u8 u16 u32 u64 }
+neg_impl_numeric! { isize i8 i16 i32 i64 f32 f64 }
 
 /// The `Not` trait is used to specify the functionality of unary `!`.
 ///

src/libcore/str/mod.rs

@@ -855,7 +855,7 @@ impl TwoWaySearcher {
     #[allow(dead_code)]
     #[allow(deprecated)]
     fn maximal_suffix(arr: &[u8], reversed: bool) -> (usize, usize) {
-        let mut left: usize = -1; // Corresponds to i in the paper
+        let mut left: usize = !0; // Corresponds to i in the paper
         let mut right = 0; // Corresponds to j in the paper
         let mut offset = 1; // Corresponds to k in the paper
         let mut period = 1; // Corresponds to p in the paper