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update isolate_highest_one for NonZero<T> #147686

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update isolate_highest_one for NonZero<T> #147686

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b639994
update isolate_highest_one for NonZero<T>
vrtgs Oct 14, 2025
a04e2f3
fix isolate_highest_one for signed NonZero<T>
vrtgs Oct 14, 2025
0ad0cae
fix compiler error where $UInt was used in place of $Uint
vrtgs Oct 14, 2025
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9 changes: 6 additions & 3 deletions library/core/src/num/nonzero.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -660,12 +660,15 @@ macro_rules! nonzero_integer {
without modifying the original"]
#[inline(always)]
pub const fn isolate_highest_one(self) -> Self {
let n = self.get() & (((1 as $Int) << (<$Int>::BITS - 1)).wrapping_shr(self.leading_zeros()));

// SAFETY:
// `self` is non-zero, so masking to preserve only the most
// significant set bit will result in a non-zero `n`.
unsafe { NonZero::new_unchecked(n) }
// and self.leading_zeros() is always < $INT::BITS since
// at least one of the bits in the number is not zero
unsafe {
let bit = (((1 as $Uint) << (<$Uint>::BITS - 1)).unchecked_shr(self.leading_zeros()));
NonZero::new_unchecked(bit as $Int)
}
}

/// Returns `self` with only the least significant bit set.
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