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Auto merge of #103406 - Jules-Bertholet:from_clone_slice_to_box, r=dtolnay

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Loosen `From<&[T]> for Box<[T]>` bound to `T: Clone`

Also loosens `From<Cow<'_, [T]>> for Box<[T]>`'s bound.

[Discussion on Zulip](https://rust-lang.zulipchat.com/#narrow/stream/219381-t-libs/topic/From.3C.26.5BT.5D.3E.20impls.20consistency)
This commit is contained in:
bors 2023-04-30 13:58:00 +00:00
commit 831c9298c8
1 changed files with 31 additions and 8 deletions
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39
library/alloc/src/boxed.rs
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@ -1455,9 +1455,36 @@ where
}
}
/// Specialization trait used for `From<&[T]>`.
#[cfg(not(no_global_oom_handling))]
trait BoxFromSlice<T> {
fn from_slice(slice: &[T]) -> Self;
}
#[cfg(not(no_global_oom_handling))]
impl<T: Clone> BoxFromSlice<T> for Box<[T]> {
#[inline]
default fn from_slice(slice: &[T]) -> Self {
slice.to_vec().into_boxed_slice()
}
}
#[cfg(not(no_global_oom_handling))]
impl<T: Copy> BoxFromSlice<T> for Box<[T]> {
#[inline]
fn from_slice(slice: &[T]) -> Self {
let len = slice.len();
let buf = RawVec::with_capacity(len);
unsafe {
ptr::copy_nonoverlapping(slice.as_ptr(), buf.ptr(), len);
buf.into_box(slice.len()).assume_init()
}
}
}
#[cfg(not(no_global_oom_handling))]
#[stable(feature = "box_from_slice", since = "1.17.0")]
impl<T: Copy> From<&[T]> for Box<[T]> {
impl<T: Clone> From<&[T]> for Box<[T]> {
/// Converts a `&[T]` into a `Box<[T]>`
///
/// This conversion allocates on the heap
@ -1471,19 +1498,15 @@ impl<T: Copy> From<&[T]> for Box<[T]> {
///
/// println!("{boxed_slice:?}");
/// ```
#[inline]
fn from(slice: &[T]) -> Box<[T]> {
let len = slice.len();
let buf = RawVec::with_capacity(len);
unsafe {
ptr::copy_nonoverlapping(slice.as_ptr(), buf.ptr(), len);
buf.into_box(slice.len()).assume_init()
}
<Self as BoxFromSlice<T>>::from_slice(slice)
}
}
#[cfg(not(no_global_oom_handling))]
#[stable(feature = "box_from_cow", since = "1.45.0")]
impl<T: Copy> From<Cow<'_, [T]>> for Box<[T]> {
impl<T: Clone> From<Cow<'_, [T]>> for Box<[T]> {
/// Converts a `Cow<'_, [T]>` into a `Box<[T]>`
///
/// When `cow` is the `Cow::Borrowed` variant, this