in which we decline to lint single-use lifetimes in derived impls

[zackmdavis]

Resolves#53738.

r? @eddyb

[zackmdavis]

(Pushing the branch directly to rust-lang/rust rather than my "fork" was a mistake, but probably an inconsequential one?)

[rust-highfive]

The job x86_64-gnu-llvm-6.0 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.

[00:04:38] travis_fold:start:tidy
travis_time:start:tidy
tidy check
[00:04:39] tidy error: /checkout/src/librustc/middle/resolve_lifetime.rs:1595: line longer than 100 chars
[00:04:44] some tidy checks failed
[00:04:44] [00:04:44] [00:04:44] command did not execute successfully: "/checkout/obj/build/x86_64-unknown-linux-gnu/stage0-tools-bin/tidy" "/checkout/src" "/checkout/obj/build/x86_64-unknown-linux-gnu/stage0/bin/cargo" "--no-vendor" "--quiet"
[00:04:44] [00:04:44] [00:04:44] failed to run: /checkout/obj/build/bootstrap/debug/bootstrap test src/tools/tidy
[00:04:44] Build completed unsuccessfully in 0:01:14
---
travis_time:end:0ce616d0:start=1560493917882537935,finish=1560493917888206705,duration=5668770
travis_fold:end:after_failure.3
travis_fold:start:after_failure.4
travis_time:start:0e1e86ed
$ 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:181b93a0
travis_time:start:181b93a0
$ 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:166925a6
$ 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]

but probably an inconsequential one?

Yep; we have branch protection on the important branches; please just cleanup after you're done. 😃

[Centril]

@scottmcm suggested on Discord that we should change the macro expansion of the built-in derives to use '_ instead. That seems like it might generate less code that might be good for perf and possibly solve this issue (but not for custom derives!). In either case, even if we land this PR in its current form, we should probably also change the expansion?

[zackmdavis]

(fixed tidy)

[petrochenkov]

Derives are a special case of "macros from other crates", which normally suppress lints.
Why doesn't that generic mechanism work here?

[oli-obk]

Derives are a special case of "macros from other crates", which normally suppress lints.
Why doesn't that generic mechanism work here?

The problem is (as explained by @estebank) that the derive doesn't mark the spans of idents it's using as coming from an expansion.

[eddyb]

@bors r+ (feel free to open an issue about changing the deriving output)

[bors]

📌 Commit 17653dd has been approved by eddyb

[bors]

🌲 The tree is currently closed for pull requests below priority 500, this pull request will be tested once the tree is reopened