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Use unchecked_sub in split_at #124699

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Merged
merged 1 commit into from
May 4, 2024
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Use unchecked_sub in split_at #124699

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11 changes: 8 additions & 3 deletions library/core/src/slice/mod.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -9,7 +9,7 @@
use crate::cmp::Ordering::{self, Equal, Greater, Less};
use crate::fmt;
use crate::hint;
use crate::intrinsics::exact_div;
use crate::intrinsics::{exact_div, unchecked_sub};
use crate::mem::{self, SizedTypeProperties};
use crate::num::NonZero;
use crate::ops::{Bound, OneSidedRange, Range, RangeBounds};
Expand Down Expand Up @@ -1983,7 +1983,7 @@ impl<T> [T] {
);

// SAFETY: Caller has to check that `0 <= mid <= self.len()`
unsafe { (from_raw_parts(ptr, mid), from_raw_parts(ptr.add(mid), len - mid)) }
unsafe { (from_raw_parts(ptr, mid), from_raw_parts(ptr.add(mid), unchecked_sub(len, mid))) }
}

/// Divides one mutable slice into two at an index, without doing bounds checking.
Expand Down Expand Up @@ -2035,7 +2035,12 @@ impl<T> [T] {
//
// `[ptr; mid]` and `[mid; len]` are not overlapping, so returning a mutable reference
// is fine.
unsafe { (from_raw_parts_mut(ptr, mid), from_raw_parts_mut(ptr.add(mid), len - mid)) }
unsafe {
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two local variables for the left and right sides would have been nice here to reduce the lines from 6 to 3 :3, things like this are certainly formative of your opinions about rustfmt 😆 (though i can't really complain, it's doing its best)

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Yeah, my preferred philosophical underpinnings for a formatter are pretty different from those that rustfmt picked :(

(
from_raw_parts_mut(ptr, mid),
from_raw_parts_mut(ptr.add(mid), unchecked_sub(len, mid)),
)
}
}

/// Divides one slice into two at an index, returning `None` if the slice is
Expand Down