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Use #[rustc_inherit_overflow_checks] instead of Add::add etc.

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This commit is contained in:
Mara Bos
2021-02-04 00:20:08 +01:00
parent 07194ffcd2
commit 053769dd53
4 changed files with 65 additions and 38 deletions
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8
library/core/src/iter/range.rs
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@@ -1,7 +1,7 @@
use crate::char;
use crate::convert::TryFrom;
use crate::mem;
use crate::ops::{self, Add, Sub, Try};
use crate::ops::{self, Try};
use super::{FusedIterator, TrustedLen};
@@ -201,11 +201,12 @@ macro_rules! step_identical_methods {
#[inline]
#[allow(arithmetic_overflow)]
#[rustc_inherit_overflow_checks]
fn forward(start: Self, n: usize) -> Self {
// In debug builds, trigger a panic on overflow.
// This should optimize completely out in release builds.
if Self::forward_checked(start, n).is_none() {
let _ = Add::add(Self::MAX, 1);
let _ = Self::MAX + 1;
}
// Do wrapping math to allow e.g. `Step::forward(-128i8, 255)`.
start.wrapping_add(n as Self)
@@ -213,11 +214,12 @@ macro_rules! step_identical_methods {
#[inline]
#[allow(arithmetic_overflow)]
#[rustc_inherit_overflow_checks]
fn backward(start: Self, n: usize) -> Self {
// In debug builds, trigger a panic on overflow.
// This should optimize completely out in release builds.
if Self::backward_checked(start, n).is_none() {
let _ = Sub::sub(Self::MIN, 1);
let _ = Self::MIN - 1;
}
// Do wrapping math to allow e.g. `Step::backward(127i8, 255)`.
start.wrapping_sub(n as Self)