Suggest using raw identifiers in 2018 edition when using keywords

[estebank]

No description provided.

[rust-highfive]

r? @petrochenkov

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[petrochenkov]

@bors r+

[bors]

📌 Commit 42c0f47116e34cc6ee8f52f57360f206be5c0c22 has been approved by petrochenkov

[bors]

⌛ Testing commit 42c0f47116e34cc6ee8f52f57360f206be5c0c22 with merge d659bcf5762178393da07258652977903e2922cb...

[bors]

💔 Test failed - status-travis

[rust-highfive]

The job dist-x86_64-musl 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.

[00:49:56] ---- [ui] ui/issues/issue-57198.rs stdout ----
[00:49:56] diff of stderr:
[00:49:56] 
[00:49:56] 3    |
[00:49:56] 4 LL |     m::for();
[00:49:56] 5    |        ^^^ expected identifier, found keyword
[00:49:56] + help: you can escape reserved keywords to use them as identifiers
[00:49:56] +    |
[00:49:56] + LL |     m::r#for();
[00:49:56] 6 
[00:49:56] 7 error: aborting due to previous error
[00:49:56] 8 
[00:49:56] 
[00:49:56] 
[00:49:56] 
[00:49:56] The actual stderr differed from the expected stderr.
[00:49:56] Actual stderr saved to /checkout/obj/build/x86_64-unknown-linux-gnu/test/ui/issues/issue-57198/issue-57198.stderr
[00:49:56] To update references, rerun the tests and pass the `--bless` flag
[00:49:56] To only update this specific test, also pass `--test-args issues/issue-57198.rs`
[00:49:56] error: 1 errors occurred comparing output.
[00:49:56] status: exit code: 1
[00:49:56] status: exit code: 1
[00:49:56] command: "/checkout/obj/build/x86_64-unknown-linux-gnu/stage2/bin/rustc" "/checkout/src/test/ui/issues/issue-57198.rs" "--target=x86_64-unknown-linux-musl" "--error-format" "json" "-Zui-testing" "-C" "prefer-dynamic" "-o" "/checkout/obj/build/x86_64-unknown-linux-gnu/test/ui/issues/issue-57198/a" "-Crpath" "-O" "-Zunstable-options" "-Lnative=/checkout/obj/build/x86_64-unknown-linux-musl/native/rust-test-helpers" "-Clinker=/musl-x86_64/bin/musl-gcc" "-L" "/checkout/obj/build/x86_64-unknown-linux-gnu/test/ui/issues/issue-57198/auxiliary" "-A" "unused"
[00:49:56] ------------------------------------------
[00:49:56] 
[00:49:56] ------------------------------------------
[00:49:56] stderr:
[00:49:56] stderr:
[00:49:56] ------------------------------------------
[00:49:56] {"message":"expected identifier, found keyword `for`","code":null,"level":"error","spans":[{"file_name":"/checkout/src/test/ui/issues/issue-57198.rs","byte_start":52,"byte_end":55,"line_start":6,"line_end":6,"column_start":8,"column_end":11,"is_primary":true,"text":[{"text":"    m::for();","highlight_start":8,"highlight_end":11}],"label":"expected identifier, found keyword","suggested_replacement":null,"suggestion_applicability":null,"expansion":null}],"children":[{"message":"you can escape reserved keywords to use them as identifiers","code":null,"level":"help","spans":[{"file_name":"/checkout/src/test/ui/issues/issue-57198.rs","byte_start":52,"byte_end":55,"line_start":6,"line_end":6,"column_start":8,"column_end":11,"is_primary":true,"text":[{"text":"    m::for();","highlight_start":8,"highlight_end":11}],"label":null,"suggested_replacement":"r#for","suggestion_applicability":"MaybeIncorrect","expansion":null}],"children":[],"rendered":null}],"rendered":"error: expected identifier, found keyword `for`\n  --> /checkout/src/test/ui/issues/issue-57198.rs:6:8\n   |\nLL |     m::for();\n   |        ^^^ expected identifier, found keyword\nhelp: you can escape reserved keywords to use them as identifiers\n   |\nLL |     m::r#for();\n   |        ^^^^^\n\n"}
[00:49:56] {"message":"aborting due to previous error","code":null,"level":"error","spans":[],"children":[],"rendered":"error: aborting due to previous error\n\n"}
[00:49:56] ------------------------------------------
[00:49:56] 
[00:49:56] thread '[ui] ui/issues/issue-57198.rs' panicked at 'explicit panic', src/tools/compiletest/src/runtest.rs:3245:9
[00:49:56] note: Run with `RUST_BACKTRACE=1` for a backtrace.
---
[00:49:56] 
[00:49:56] thread 'main' panicked at 'Some tests failed', src/tools/compiletest/src/main.rs:495:22
[00:49:56] 
[00:49:56] 
[00:49:56] command did not execute successfully: "/checkout/obj/build/x86_64-unknown-linux-gnu/stage0-tools-bin/compiletest" "--compile-lib-path" "/checkout/obj/build/x86_64-unknown-linux-gnu/stage2/lib" "--run-lib-path" "/checkout/obj/build/x86_64-unknown-linux-gnu/stage2/lib/rustlib/x86_64-unknown-linux-musl/lib" "--rustc-path" "/checkout/obj/build/x86_64-unknown-linux-gnu/stage2/bin/rustc" "--src-base" "/checkout/src/test/ui" "--build-base" "/checkout/obj/build/x86_64-unknown-linux-gnu/test/ui" "--stage-id" "stage2-x86_64-unknown-linux-musl" "--mode" "ui" "--target" "x86_64-unknown-linux-musl" "--host" "x86_64-unknown-linux-gnu" "--llvm-filecheck" "/checkout/obj/build/x86_64-unknown-linux-gnu/llvm/build/bin/FileCheck" "--linker" "/musl-x86_64/bin/musl-gcc" "--host-rustcflags" "-Crpath -O -Zunstable-options  -Lnative=/checkout/obj/build/x86_64-unknown-linux-gnu/native/rust-test-helpers" "--target-rustcflags" "-Crpath -O -Zunstable-options  -Lnative=/checkout/obj/build/x86_64-unknown-linux-musl/native/rust-test-helpers" "--docck-python" "/usr/bin/python2.7" "--lldb-python" "/usr/bin/python2.7" "--gdb" "/usr/bin/gdb" "--llvm-version" "8.0.0svn\n" "--cc" "" "--cxx" "" "--cflags" "" "--llvm-components" "" "--llvm-cxxflags" "" "--adb-path" "adb" "--adb-test-dir" "/data/tmp/work" "--android-cross-path" "" "--color" "always"
[00:49:56] 
[00:49:56] 
[00:49:56] failed to run: /checkout/obj/build/bootstrap/debug/bootstrap test --target x86_64-unknown-linux-musl
[00:49:56] Build completed unsuccessfully in 0:48:03
---
travis_time:end:1faa4569:start=1546266586385388138,finish=1546266586395825473,duration=10437335
travis_fold:end:after_failure.3
travis_fold:start:after_failure.4
travis_time:start:0581c344
$ 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
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travis_time:start:0da90481
travis_time:start:0da90481
$ 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:0b147694
$ 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)

[petrochenkov]

@estebank
After some thought, maybe raw identifiers need to be recommended only for edition-specific keywords?
IMO, raw identifiers are more an emergency feature, than something that should be used casually.

[estebank]

@petrochenkov that sounds reasonable to me. I want to give people a chance to find out about the feature, but not to overuse it... Maybe not even using a suggestion but just linking to the book could be a good alternative. Higher barrier to finding than just accepting a change, while also having a chance to find out about them. The drawback is that I have seen people (particularly medium-experienced devs) ignoring the links even when they'd include a bit of info they wouldn't know. Maybe just an old school help message informing on raw idents while steering people away from them?

[petrochenkov]

Er, I don't think too much about this.
I'd personally limit this to edition-specific keywords or just keep as is.

@bors r+

[bors]

📌 Commit 18e0bda has been approved by petrochenkov

[bors]

⌛ Testing commit 18e0bda with merge 443ae75...

[bors]

☀️ Test successful - status-appveyor, status-travis
Approved by: petrochenkov
Pushing 443ae75 to master...