1use core::iter::TrustedLen;
2use core::slice::{self};
3
4use super::{IntoIter, Vec};
5use crate::alloc::Allocator;
6
7// Specialization trait used for Vec::extend
8pub(super) trait SpecExtend<T, I> {
9 #[track_caller]
10 fn spec_extend(&mut self, iter: I);
11}
12
13impl<T, I, A: Allocator> SpecExtend<T, I> for Vec<T, A>
14where
15 I: Iterator<Item = T>,
16{
17 #[track_caller]
18 default fn spec_extend(&mut self, iter: I) {
19 self.extend_desugared(iterator:iter)
20 }
21}
22
23impl<T, I, A: Allocator> SpecExtend<T, I> for Vec<T, A>
24where
25 I: TrustedLen<Item = T>,
26{
27 #[track_caller]
28 default fn spec_extend(&mut self, iterator: I) {
29 self.extend_trusted(iterator)
30 }
31}
32
33impl<T, A: Allocator> SpecExtend<T, IntoIter<T>> for Vec<T, A> {
34 #[track_caller]
35 fn spec_extend(&mut self, mut iterator: IntoIter<T>) {
36 unsafe {
37 self.append_elements(iterator.as_slice() as _);
38 }
39 iterator.forget_remaining_elements();
40 }
41}
42
43impl<'a, T: 'a, I, A: Allocator> SpecExtend<&'a T, I> for Vec<T, A>
44where
45 I: Iterator<Item = &'a T>,
46 T: Clone,
47{
48 #[track_caller]
49 default fn spec_extend(&mut self, iterator: I) {
50 self.spec_extend(iter:iterator.cloned())
51 }
52}
53
54impl<'a, T: 'a, A: Allocator> SpecExtend<&'a T, slice::Iter<'a, T>> for Vec<T, A>
55where
56 T: Copy,
57{
58 #[track_caller]
59 fn spec_extend(&mut self, iterator: slice::Iter<'a, T>) {
60 let slice: &[T] = iterator.as_slice();
61 unsafe { self.append_elements(slice) };
62 }
63}
64

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