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Rollup merge of #120110 - invpt:patch-1, r=the8472

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Update documentation for Vec::into_boxed_slice to be more clear about excess capacity

Currently, the documentation for Vec::into_boxed_slice says that "if the vector has excess capacity, its items will be moved into a newly-allocated buffer with exactly the right capacity." This is misleading, as copies do not necessarily occur, depending on if the allocator supports in-place shrinking. I copied some of the wording from shrink_to_fit, though it could potentially still be worded better than this.
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Matthias Krüger 2024-01-19 08:15:05 +01:00 committed by GitHub
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1 changed files with 12 additions and 7 deletions
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library/alloc/src/vec/mod.rs
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@ -358,7 +358,7 @@
/// ///
/// `vec![x; n]`, `vec![a, b, c, d]`, and /// `vec![x; n]`, `vec![a, b, c, d]`, and
/// [`Vec::with_capacity(n)`][`Vec::with_capacity`], will all produce a `Vec` /// [`Vec::with_capacity(n)`][`Vec::with_capacity`], will all produce a `Vec`
/// with exactly the requested capacity. If <code>[len] == [capacity]</code>, /// with at least the requested capacity. If <code>[len] == [capacity]</code>,
/// (as is the case for the [`vec!`] macro), then a `Vec<T>` can be converted to /// (as is the case for the [`vec!`] macro), then a `Vec<T>` can be converted to
/// and from a [`Box<[T]>`][owned slice] without reallocating or moving the elements. /// and from a [`Box<[T]>`][owned slice] without reallocating or moving the elements.
/// ///
@ -1023,8 +1023,11 @@ pub fn try_reserve_exact(&mut self, additional: usize) -> Result<(), TryReserveE
/// Shrinks the capacity of the vector as much as possible. /// Shrinks the capacity of the vector as much as possible.
/// ///
/// It will drop down as close as possible to the length but the allocator /// The behavior of this method depends on the allocator, which may either shrink the vector
/// may still inform the vector that there is space for a few more elements. /// in-place or reallocate. The resulting vector might still have some excess capacity, just as
/// is the case for [`with_capacity`]. See [`Allocator::shrink`] for more details.
///
/// [`with_capacity`]: Vec::with_capacity
/// ///
/// # Examples /// # Examples
/// ///
@ -1074,10 +1077,10 @@ pub fn shrink_to(&mut self, min_capacity: usize) {
/// Converts the vector into [`Box<[T]>`][owned slice]. /// Converts the vector into [`Box<[T]>`][owned slice].
/// ///
/// If the vector has excess capacity, its items will be moved into a /// Before doing the conversion, this method discards excess capacity like [`shrink_to_fit`].
/// newly-allocated buffer with exactly the right capacity.
/// ///
/// [owned slice]: Box /// [owned slice]: Box
/// [`shrink_to_fit`]: Vec::shrink_to_fit
/// ///
/// # Examples /// # Examples
/// ///
@ -3290,8 +3293,10 @@ fn from(s: Box<[T], A>) -> Self {
impl<T, A: Allocator> From<Vec<T, A>> for Box<[T], A> { impl<T, A: Allocator> From<Vec<T, A>> for Box<[T], A> {
/// Convert a vector into a boxed slice. /// Convert a vector into a boxed slice.
/// ///
/// If `v` has excess capacity, its items will be moved into a /// Before doing the conversion, this method discards excess capacity like [`Vec::shrink_to_fit`].
/// newly-allocated buffer with exactly the right capacity. ///
/// [owned slice]: Box
/// [`Vec::shrink_to_fit`]: Vec::shrink_to_fit
/// ///
/// # Examples /// # Examples
/// ///