suggestion-diagnostics: as_ref improve snippet

[dlrobertson]

Improve the code snippet suggested in suggestion-diagnostics when
suggesting the use of as_ref.

Given:

fn test(x: &usize) {}
fn main() {
    Some(42).map(|x| test(x));
}

Suggest

  help: consider using `as_ref` instead: `as_ref().map`

Instead of

  help: consider using `as_ref` instead: `as_ref().`

[rust-highfive]

r? @eddyb

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

[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.

travis_time:end:04ee9a5e:start=1546978089151273248,finish=1546978090321928223,duration=1170654975
$ git checkout -qf FETCH_HEAD
travis_fold:end:git.checkout

Encrypted environment variables have been removed for security reasons.
See https://docs.travis-ci.com/user/pull-requests/#pull-requests-and-security-restrictions
$ export SCCACHE_BUCKET=rust-lang-ci-sccache2
$ export SCCACHE_REGION=us-west-1
Setting environment variables from .travis.yml
$ export IMAGE=x86_64-gnu-llvm-6.0
---

[00:05:08] travis_fold:start:tidy
travis_time:start:tidy
tidy check
[00:05:08] tidy error: /checkout/src/librustc_typeck/check/demand.rs:195: line longer than 100 chars
[00:05:10] some tidy checks failed
[00:05:10] 
[00:05:10] 
[00:05:10] 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"
[00:05:10] 
[00:05:10] 
[00:05:10] failed to run: /checkout/obj/build/bootstrap/debug/bootstrap test src/tools/tidy
[00:05:10] Build completed unsuccessfully in 0:00:45
[00:05:10] Build completed unsuccessfully in 0:00:45
[00:05:10] Makefile:69: recipe for target 'tidy' failed
[00:05:10] make: *** [tidy] Error 1
The command "stamp sh -x -c "$RUN_SCRIPT"" exited with 2.
travis_time:start:094e3067
$ date && (curl -fs --head https://google.com | grep ^Date: | sed 's/Date: //g' || true)
Tue Jan  8 20:13:40 UTC 2019
---
travis_time:end:0148d452:start=1546978421677496844,finish=1546978421682105515,duration=4608671
travis_fold:end:after_failure.3
travis_fold:start:after_failure.4
travis_time:start:03c82578
$ 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:2f41bc7b
travis_time:start:2f41bc7b
$ 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:0247d91f
$ 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)

[estebank]

Formatting:

    fn can_use_as_ref(
        &self,
        expr: &hir::Expr,
        cm: &SourceMap,
    ) -> Option<(Span, &'static str, String)> {

[TimNN]

Ping from triage @dlrobertson: Some changes have been requested to your PR.

[TimNN]

Also, @estebank: Can you review this PR? It seems like @eddyb is unavailable at the moment.

[estebank]

r? @estebank

[dlrobertson]

👍 thanks for the ping. I'll look at this tonight.

[dlrobertson]

@estebank updated

[estebank]

r=me once the nitpick is addressed :)

[dlrobertson]

@bors r=estebank

[bors]

@dlrobertson: 🔑 Insufficient privileges: Not in reviewers

[dlrobertson]

@estebank looks like you'll need to r or delegate the PR... Unless I missed something.

[estebank]

@bors r+

[bors]

📌 Commit 285d4a7 has been approved by estebank