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vec: Use SpecCloneIntoVec::clone_into to implement Vec::clone_from

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In the past, Vec::clone_from was implemented using slice::clone_into.
The code from clone_into was later duplicated into clone_from in
8725e4c337, which is the commit that adds custom allocator support to
Vec. Presumably this was done because the slice::clone_into only works
for vecs with the default allocator so it would have the wrong type to
clone into Vec<T, A>.

Now that the clone_into implementation is moved out into a specializable
trait anyway we might as well use that to share the code between the two
methods.
This commit is contained in:
Neil Roberts 2023-01-28 14:52:31 +01:00
parent ba80c662f4
commit a34f11c006
1 changed files with 1 additions and 30 deletions
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31
library/alloc/src/vec/mod.rs
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@ -2646,35 +2646,6 @@ impl<T, A: Allocator> ops::DerefMut for Vec<T, A> {
}
}
#[cfg(not(no_global_oom_handling))]
trait SpecCloneFrom {
fn clone_from(this: &mut Self, other: &Self);
}
#[cfg(not(no_global_oom_handling))]
impl<T: Clone, A: Allocator> SpecCloneFrom for Vec<T, A> {
default fn clone_from(this: &mut Self, other: &Self) {
// drop anything that will not be overwritten
this.truncate(other.len());
// self.len <= other.len due to the truncate above, so the
// slices here are always in-bounds.
let (init, tail) = other.split_at(this.len());
// reuse the contained values' allocations/resources.
this.clone_from_slice(init);
this.extend_from_slice(tail);
}
}
#[cfg(not(no_global_oom_handling))]
impl<T: Copy, A: Allocator> SpecCloneFrom for Vec<T, A> {
fn clone_from(this: &mut Self, other: &Self) {
this.clear();
this.extend_from_slice(other);
}
}
#[cfg(not(no_global_oom_handling))]
#[stable(feature = "rust1", since = "1.0.0")]
impl<T: Clone, A: Allocator + Clone> Clone for Vec<T, A> {
@ -2695,7 +2666,7 @@ impl<T: Clone, A: Allocator + Clone> Clone for Vec<T, A> {
}
fn clone_from(&mut self, other: &Self) {
SpecCloneFrom::clone_from(self, other)
crate::slice::SpecCloneIntoVec::clone_into(other.as_slice(), self);
}
}