Why does std::vec::Vec::to_vec() exist?

std::vec::Vec also implements the Clone trait, so a Vec can be copied with ::clone(). Why does it also provide ::to_vec()?

Generally, I would expect common trait methods for common functionality to be preferred over harder-to-remember per-type method names.

If this were some pre-Clone legacy method, I'd expect it to be marked deprecated. But it does not appear to be marked so.


Edit: Context: rustc 1.43.1 prompted me to copy a &Vec<u8> to Vec<u8> with to_vec(), when it seems like clone() is (arguably) better:

    |        ^^^^
    |        |
    |        expected struct `std::vec::Vec`, found reference
    |        help: try using a conversion method: `data.to_vec()`

to_vec is not a method of the Vec type, but a method of the [T] or “slice” type. It can be called on any type that derefs to a slice, including Vec.


Thanks. I was confused because all of the slice methods show up on https://doc.rust-lang.org/std/vec/struct.Vec.html . It seems this is because Vec implements Deref<Target = [T]>?

Edit: And the documentation is not super clear (to me!) on an individual method basis what the current impl is.

Yes, that's correct.

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Thanks! Is this something we could document better, or already something that has been considered and dismissed?

It could probably be improved. One problem is when a doc page gets so long that the section header is off-screen after scrolling to a specific method, making it impossible to see the full context. Keeping this information visible would be really useful.


Yeah, that would be a nice way to solve the problem. I tend to be an old HTML4 curmudgeon and would just throw the impl inline with every single method, but a top bar that follows down the page would also be easy to understand for me.

Thanks again. I'm about 8 days into Rust and still getting familiar with the basics like this.

CSS has position: sticky, which could certainly be used. It's supported in all modern browsers.


Just to follow up on my previous comment, adding the following CSS to any page on docs.rs does the trick

.small-section-header {
    position: sticky;
    top: 0;
    z-index: 2;
    background-color: #353535;

Naturally, the background-color will need to change alongside the theme. The expand/collapse button is still visible underneath this, as the element doesn't sit far enough to the left. But as a quick fix, this little snippet of code suffices (and in my opinion is actually far better).


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