Add [T]::swap_with_slice

[scottmcm]

The safe version of a method from ptr, like [T]::copy_from_slice is.

Tracking issue: #44030

[rust-highfive]

r? @brson

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[alexcrichton]

Seems like a nifty API to me, thanks!

@rust-lang/libs, any thoughts on naming here?

I'd sort of be in favor of swap_slice as opposed to swap_with_slice?

[scottmcm]

I chose swap_with_slice here for differentiation with [T]::swap(usize, usize) and for similarity with copy_from_slice (which isn't copy_slice), but I'm happy to change it to whatever.

[aturon]

I'm ambivalent on the naming, but slightly favor @scottmcm's proposed naming.

[alexcrichton]

IIRC copy_from_slice was selected to ensure the direction of the copy was clear, although with a swap it's less important as the direction shouldn't matter? I don't necessarily dislike swap_with_slice, I just wasn't sure where with came from!

[scottmcm]

Oh, right, clone_from_slice is Clone::clone_from + "this takes a slice". That does seem to argue for swap_slice = mem::swap + "this takes a slice". The preposition isn't really needed.

I guess this with is sortof like SliceExt::ends_with or intrinsics::add_with_overflow, but very different from the withs in Vec::with_capacity or Entry::or_insert_with...

[alexcrichton]

Eh and to be clear I'm not opposed to the name at all, just wanted to pontificate for a bit before merging.

[alexcrichton]

Ok well sounds like there aren't many other thoughts, so let's just decide this before stabilization

@bors: r+

[bors]

📌 Commit c4cb2d1 has been approved by alexcrichton

[bors]

⌛ Testing commit c4cb2d1 with merge ba65645...

[bors]

☀️ Test successful - status-appveyor, status-travis
Approved by: alexcrichton
Pushing ba65645 to master...