Initial draft of copy ergonomics design note

[Mark-Simulacrum]

This draws mostly on readily available links in rust-lang/rust#44619.

r? @nikomatsakis

cc @rust-lang/lang

[Mark-Simulacrum]

I plan to open a second PR for the autoderef/autoref on operators, since it feels fairly orthogonal to copy ergonomics in general.

[scottmcm]

Thanks for writing this up!

@Mark-Simulacrum Annoyingly the GitHub UI refused to let me suggest additions as a PR, so I just pushed it. Feel free to rebase-disappear the updates if you dislike them.

[Mark-Simulacrum]

Please feel free to push :)

Definitely not intended as a complete work.

[Mark-Simulacrum]

I think CI failure is just because I added coroutines to SUMMARY.md (previously they weren't being checked looks like) -- maybe @samsartor can take a look and patch that up?

[samsartor]

I think CI failure is just because I added coroutines to SUMMARY.md (previously they weren't being checked looks like) -- maybe @samsartor can take a look and patch that up?

Yep, I totally missed that we were using mdbook. Just made #64 to fix that.

[nikomatsakis]

This is a great start! I have a few suggestions.

[Mark-Simulacrum]

Added a few examples, as you suggested.

[Mark-Simulacrum]

OK, I think this is ready to go -- updated per all the feedback given so far. r? @pnkfelix for another review?

[pnkfelix]

This looks good to me. I'm inclined to merge it as is.