Suggest valid crate type if invalid crate type is found

[phansch]

This adds a suggestion to the invalid_crate_types lint.

The suggestion is based on the Levenshtein distance to existing crate
types. If no suggestion is found it will show the lint without any
suggestions.

Closes#53958

[rust-highfive]

r? @davidtwco

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

[phansch]

Should this be a machine applicable suggestion? I'm not really sure if the Levenshtein candidate is good enough in this case because cdylib, dylib, rlib and lib are pretty close to each other.

[rust-highfive]

The job x86_64-gnu-llvm-5.0 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_driver/driver.rs:1525: line longer than 100 chars
[00:04:39] tidy error: /checkout/src/librustc_driver/driver.rs:1533: line longer than 100 chars
[00:04:40] some tidy checks failed
[00:04:40] [00:04:40] [00:04:40] 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"
[00:04:40] [00:04:40] [00:04:40] failed to run: /checkout/obj/build/bootstrap/debug/bootstrap test src/tools/tidy
[00:04:40] Build completed unsuccessfully in 0:00:49
[00:04:40] Build completed unsuccessfully in 0:00:49
[00:04:40] make: *** [tidy] Error 1
[00:04:40] Makefile:79: recipe for target 'tidy' failed
The command "stamp sh -x -c "$RUN_SCRIPT"" exited with 2.
travis_time:start:0a75dbec
$ date && (curl -fs --head https://google.com | grep ^Date: | sed 's/Date: //g' || true)
---
travis_time:end:01901004:start=1536822065529320655,finish=1536822065534486284,duration=5165629
travis_fold:end:after_failure.3
travis_fold:start:after_failure.4
travis_time:start:112fd12a
$ 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 -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:02bfb2e2
travis_time:start:02bfb2e2
$ 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:05e379e2
$ 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)

[davidtwco]

Should this be a machine applicable suggestion? I'm not really sure if the Levenshtein candidate is good enough in this case because cdylib, dylib, rlib and lib are pretty close to each other.

I think Applicability::MaybeIncorrect is a good choice here, the suggestion is likely correct but it might not be - this seems similar to other uses I can find of Applicability::MaybeIncorrect.

---

Otherwise, this looks good to me. Assigning someone else to take another look who might be more familiar with this part of the code.

r? @oli-obk (based on github's suggestions)

[phansch]

I think @oli-obk is on holiday until October, so maybe.. r? @estebank
(will fix tidy + machine applicable suggestion later today)

[estebank]

Minor changes requested. r=me after changing.

[estebank]

Notice that the span includes the "s, but the suggestion doesn't, which would make applying this suggestion generate the code #![crate_type=staticlib], which is incorrect. Easiest solution is to include the quotes in the suggestion.

[estebank]

Change to

lint::builtin::BuiltinLintDiagnostics::UnknownCrateTypes(
span,
"did you mean".to_string(),
format!("\"{}\"", candidate),
);

[estebank]

As noted in the prior discussion, use span_suggestion_with_applicability. MaybeIncorrect is always a safe bet to use, MachineApplicable is not consistently used throughout the codebase. It sometimes means 100% certainty, while others it means "95% of the cases this error fires, this suggestion is correct". I'm ok with the overly restrictive reading of the meaning.

[estebank]

This line is too long, reformat.

[phansch]

I sort of did a rebase by accident instead of adding new commits, but it should be all good now 👍

[estebank]

@bors r+ rollup

[bors]

📌 Commit 7249a1b has been approved by estebank