[beta] Do not accidentally treat multi-segment meta-items as single-segment

[petrochenkov]

Partial backport of #58899 to beta

[rust-highfive]

r? @eddyb

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[rust-highfive]

⚠️ Warning ⚠️

• Pull requests are usually filed against the master branch for this repo, but this one is against beta. Please double check that you specified the right target!

[pnkfelix]

Discussed at T-compiler meeting. We are inclined towards a lukewarm beta-accept

Why lukewarm:

• it would have been nice if some of the extraneous changes were not part of the PR, just to make it more immediately clear on casual review what all the effects of this PR actually are.
• it is not clear if any of the bugs fixed by this are ultra-high priority.
  • Our understanding is that it is fixing a set of stable-to-stable regressions. proc_macro_derive(attributes(path::to)) both does and doesn't work #55168 is listed on PR Do not accidentally treat multi-segment meta-items as single-segment #58899. I do not know what the other ones are.
  • While such regressions are of course bad, we do have a history of letting old stable-to-stable regressions lie unfixed, under the assumption that if the users have gotten by this long without a fix, they can wait the additional 6-weeks for the trains to roll the code out.

Having said that, we trust @petrochenkov wouldn't have put the work into making this PR if it wasn't actually important.

However, I also want to make sure this PR gets a proper review to make sure that the changes it makes are the right subset of #58899.

So:

• I am reassigning it to @estebank for review.
• Once that review is done, then @petrochenkov can feel free to mark as beta-accepted.

[pnkfelix]

r? @estebank

[petrochenkov]

it would have been nice if some of the extraneous changes were not part of the PR

The extraneous changes should be left in #58899, everything here should be necessary due to removal of the old methods.
I've noticed the expand.rs change was mentioned on Zulip, but that's probably the only change that slipped through.

[estebank]

For a follow up PR, I see this pattern in multiple places, it'd be nice to add a method get_word_ident() to nested_meta so you can use if let everywhere the alternative is discarded/an error.

[estebank]

@bors r+

[bors]

📌 Commit f8b17c5 has been approved by estebank

[Centril]

@bors p=1

[bors]

⌛ Testing commit f8b17c5 with merge 2df55de6ccdb886fd78e76a80840ee9896816bb1...

[bors]

💔 Test failed - checks-travis

[rust-highfive]

The job arm-android of your PR failed on Travis (raw log). Through arcane magic we have determined that the following fragments from the build log may contain information about the problem.

Click to expand the log.

[01:51:22] test string::test_str_truncate ... ok
[01:51:22] test str::test_unsafe_slice ... ok
[01:51:22] test string::test_str_truncate_invalid_len ... ok
[01:51:22] test string::test_str_truncate_split_codepoint ... ok
[01:51:23] died due to signal 11
[01:51:23] 
[01:51:23] 
[01:51:23] command did not execute successfully: "/checkout/obj/build/x86_64-unknown-linux-gnu/stage0/bin/cargo" "test" "--target" "arm-linux-androideabi" "-j" "4" "--release" "--locked" "--color" "always" "--features" "panic-unwind backtrace" "--manifest-path" "/checkout/src/libstd/Cargo.toml" "-p" "alloc" "--"
[01:51:23] expected success, got: exit code: 3
---
travis_time:end:00f8a27c:start=1553583100392403140,finish=1553583100403478382,duration=11075242
travis_fold:end:after_failure.3
travis_fold:start:after_failure.4
travis_time:start:0923f6dc
$ ln -s . checkout && for CORE in obj/cores/core.*; do EXE=$(echo $CORE | sed 's|obj/cores/core\.[0-9]*\.!checkout!\(.*\)|\1|;y|!|/|'); if [ -f "$EXE" ]; then printf travis_fold":start:crashlog\n\033[31;1m%s\033[0m\n" "$CORE"; gdb --batch -q -c "$CORE" "$EXE" -iex 'set auto-load off' -iex 'dir src/' -iex 'set sysroot .' -ex bt -ex q; echo travis_fold":"end:crashlog; fi; done || true
travis_fold:end:after_failure.4
travis_fold:start:after_failure.5
travis_time:start:0287c6e0
travis_time:start:0287c6e0
$ cat ./obj/build/x86_64-unknown-linux-gnu/native/asan/build/lib/asan/clang_rt.asan-dynamic-i386.vers || true
cat: ./obj/build/x86_64-unknown-linux-gnu/native/asan/build/lib/asan/clang_rt.asan-dynamic-i386.vers: No such file or directory
travis_fold:end:after_failure.5
travis_fold:start:after_failure.6
travis_time:start:25295c00
$ dmesg | grep -i kill

I'm a bot! I can only do what humans tell me to, so if this was not helpful or you have suggestions for improvements, please ping or otherwise contact @TimNN. (Feature Requests)

[Centril]

@bors retry #55861

[bors]

⌛ Testing commit f8b17c5 with merge 88acdb5...

[bors]

☀️ Test successful - checks-travis, status-appveyor
Approved by: estebank
Pushing 88acdb5 to beta...