Clarify Vec::extend_from_slice doc

[tbu-]

Calling vec.extend(slice.iter().cloned()) calls the same code thanks to specialization.

I don't know of any plans to deprecate this method.

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[rust-log-analyzer]

The job aarch64-gnu-llvm-20-1 failed! Check out the build log: (web) (plain enhanced) (plain)

Click to see the possible cause of the failure (guessed by this bot)

[RUSTC-TIMING] panic_abort test:false 0.044
   Compiling cfg-if v1.0.4
[RUSTC-TIMING] cfg_if test:false 0.030
   Compiling rustc-demangle v0.1.26
error[E0271]: type mismatch resolving `<Iter<'_, T> as IntoIterator>::Item == T`
    --> library/alloc/src/vec/mod.rs:3436:21
     |
3371 | impl<T: Clone, A: Allocator> Vec<T, A> {
     |      - expected this type parameter
...
3436 |         self.extend(other.iter())
     |              ------ ^^^^^^^^^^^^ expected type parameter `T`, found `&T`
     |              |
     |              required by a bound introduced by this call
     |
     = note: expected type parameter `_`
                     found reference `&_`
note: the method call chain might not have had the expected associated types
    --> library/alloc/src/vec/mod.rs:3435:48
     |
3435 |     pub fn extend_from_slice(&mut self, other: &[T]) {
     |                                                ^^^^ `IntoIterator::Item` is `&T` here
3436 |         self.extend(other.iter())
     |                           ------ `IntoIterator::Item` remains `&T` here
note: required by a bound in `extend`
    --> library/core/src/iter/traits/collect.rs:413:31
     |
 413 |     fn extend<T: IntoIterator<Item = A>>(&mut self, iter: T);
     |                               ^^^^^^^^ required by this bound in `Extend::extend`

[RUSTC-TIMING] memchr test:false 1.338
   Compiling rustc-literal-escaper v0.0.7
[RUSTC-TIMING] rustc_literal_escaper test:false 0.190

[tbu-]

Hmm, that fails the run. I guess I have to investigate a little more.

[joboet]

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[rustbot]

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