Implement AsMut for Vec

[bluss]

Implement AsMut for Vec

Fixes#28549

[rust-highfive]

r? @alexcrichton

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[bluss]

I don't foresee any problems with this trait impl. Vec already implements AsRef, so it should impl AsMut.

Not handling Box since Box is missing both AsRef and AsMut. I thought we had a problem implementing them already, but I can't find any trace of it?

[alexcrichton]

@bors: r+ 9b97264

[alexcrichton]

We currently don't implement this for Box<T> because the meaning of as_ref on Box<Option<T>> would change (returning &Option<T> instead of Option<&T>). Which is to say it conflicts with Option::as_ref unfortunately.

Some discussion of this is happening on #27197 as well.

[bluss]

Updated with AsMut<Vec<T>>.

[alexcrichton]

@bors: r+ 804efda

[bluss]

Thanks!

[bluss]

What about implementing AsRef<[T]> for Box<[T]> (and AsMut)? It's less general than implementing it for all Box<T>, but this should be without conflict.

[alexcrichton]

Certainly a possibility to consider!

[bors]

⌛ Testing commit 804efda with merge 219eca1...

[bors]

☀️ Test successful - auto-linux-32-nopt-t, auto-linux-32-opt, auto-linux-64-nopt-t, auto-linux-64-opt, auto-linux-64-x-android-t, auto-mac-32-opt, auto-mac-64-nopt-t, auto-mac-64-opt, auto-win-gnu-32-nopt-t, auto-win-gnu-32-opt, auto-win-gnu-64-nopt-t, auto-win-gnu-64-opt, auto-win-msvc-32-opt, auto-win-msvc-64-opt