Give more detail about eq in book about enums

[mdinger]

Second try to address #21196 . A lot that was removed at the end basically seemed repetitive showing simple variations on the same type. It seems more effective to just show more variants at the beginning instead.

If you want to pack values into an example, better to use i32 or some digit than String because you don't need the to_string() method.

I didn't mention derive because:

• I can't explain it (only use it)
• I don't have a link to a good description (maybe rustbyexample but you probably want links internal)
• Giving more detail especially stating that == won't work and why should help quite a bit

I didn't make test or check links but I will if this will be merged.

@steveklabnik

[rust-highfive]

r? @pcwalton

(rust_highfive has picked a reviewer for you, use r? to override)

[mdinger]

r? @steveklabnik

[steveklabnik]

you don't need the comma here

[mdinger]

fixed

[steveklabnik]

Thanks for this @mdinger ! I think that conceptually, I like this patch. We need to do some wordsmithing, but I like the general approach.

[mdinger]

Oh good. Thanks for the quick look over. Long lead times get frustrating.

Actually, I think I may be able to work in #[derive(...)] but I gotta think about it. The way it's usually used, it tends to feel like black magic. Flip the switch and everything works but we don't explain how.

[steveklabnik]

Yeah, I'm at an airport right now, about to fly from Europe to Australia, so apologies if there ends up being a longer time for reviewing. For the benefit of other committers, since this is mostly grammar nitpicking, I'm comfortable r+ing this, since I'm going to end up doing a full editing pass later, and it is just nitpicks.

Actually, I think I may be able to work in #[derive(...)]

I don't think that's a good idea: we haven't covered any of the relevant information yet.

[mdinger]

Okay. I'll do make check and check the links in the morning.

I do tend to agree but this still leaves it open to the reader deciding "I want to define Ordering myself". But it'll just have to be dealt with, at least for now.

By the way, you guys typically have amazing response times. Especially when it's just a few minutes and since you deal with 100's of emails a day.

[steveklabnik]

By the way, you guys typically have amazing response times. Especially when it's just a few minutes and since you deal with 100's of emails a day.

Thanks. 😄

[mdinger]

make check passed and the links work. I don't know what this formatting note means but it didn't error. The formatting section looks different now. Weird.

check: formatting
...
249 error codes
highest error code: E0315

@steveklabnik r?

[steveklabnik]

@bors: r+ a9583d6

[bors]

⌛ Testing commit a9583d6 with merge 581b4f1...

[bors]

💔 Test failed - auto-mac-64-nopt-t

[alexcrichton]

@bors: retry

[bors]

⌛ Testing commit a9583d6 with merge 7884eb8...

[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-32-nopt-t, auto-win-32-opt, auto-win-64-nopt-t, auto-win-64-opt