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SmolStrBuilder: move rather than alloc + copy on finish #21194

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SmolStrBuilder: move rather than alloc + copy on finish #21194

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8 changes: 4 additions & 4 deletions lib/smol_str/src/lib.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -875,17 +875,17 @@ impl SmolStrBuilder {

/// Builds a [`SmolStr`] from `self`.
#[must_use]
pub fn finish(&self) -> SmolStr {
SmolStr(match &self.0 {
&SmolStrBuilderRepr::Inline { len, buf } => {
pub fn finish(self) -> SmolStr {
SmolStr(match self.0 {
SmolStrBuilderRepr::Inline { len, buf } => {
debug_assert!(len <= INLINE_CAP);
Repr::Inline {
// SAFETY: We know that `value.len` is less than or equal to the maximum value of `InlineSize`
len: unsafe { InlineSize::transmute_from_u8(len as u8) },
buf,
}
}
SmolStrBuilderRepr::Heap(heap) => Repr::new(heap),
SmolStrBuilderRepr::Heap(heap) => Repr::Heap(Arc::from(heap.into_boxed_str())),
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@ChayimFriedman2 ChayimFriedman2 Dec 2, 2025

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This will allocate more, not less. Arc::from will allocate anyway, so this just has the extra allocation for into_boxed_str().

})
}

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