Avoid some common false positives in intra doc link checking

[Manishearth]

The empty string case is never going to be a link. The numeric case may be a link, but if it were it would have resolved locally. It's more likely the makeshift markdown footnote notation ([0], etc)

r? @QuietMisdreavus

[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:00ce1cda:start=1552108483731564947,finish=1552108484615711045,duration=884146098
$ 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
$ export GCP_CACHE_BUCKET=rust-lang-ci-cache
Setting environment variables from .travis.yml
---
[00:56:56]    Compiling rustdoc v0.0.0 (/checkout/src/librustdoc)
[00:57:01] error[E0615]: attempted to take value of method `chars` on type `std::string::String`
[00:57:01]    --> src/librustdoc/passes/collect_intra_doc_links.rs:302:25
[00:57:01]     |
[00:57:01] 302 |             if ori_link.chars.first().unwrap().is_numeric() {
[00:57:01]     |                         ^^^^^ help: use parentheses to call the method: `chars()`
[00:57:01] error: aborting due to previous error
[00:57:01] 
[00:57:01] For more information about this error, try `rustc --explain E0615`.
[00:57:01] error: Could not compile `rustdoc`.

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)

[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:32d63af5:start=1552113615040351762,finish=1552113615929897456,duration=889545694
$ 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
$ export GCP_CACHE_BUCKET=rust-lang-ci-cache
Setting environment variables from .travis.yml
---
[00:57:35]    Compiling parking_lot_core v0.4.0
[00:57:40]    Compiling tempfile v3.0.5
[00:57:42]    Compiling parking_lot v0.7.1
[00:57:43]    Compiling rustdoc v0.0.0 (/checkout/src/librustdoc)
[00:57:48] error[E0599]: no method named `first` found for type `std::str::Chars<'_>` in the current scope
[00:57:48]     |
[00:57:48]     |
[00:57:48] 302 |             if ori_link.chars().first().unwrap().is_numeric() {
[00:57:48] 
[00:57:49] error: aborting due to previous error
[00:57:49] 
[00:57:49] For more information about this error, try `rustc --explain E0599`.
---
travis_time:end:05a780d6:start=1552117096005320376,finish=1552117096012714702,duration=7394326
travis_fold:end:after_failure.4
travis_fold:start:after_failure.5
travis_time:start:0337a408
$ 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:066356d0
$ 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)

[euclio]

I'm not sure that I agree with silencing the warning for footnotes. I personally would want to be warned that my footnote link isn't resolving to anything. Maybe there could be a note/help suggesting to add a link if it looks like a footnote?

[Manishearth]

Footnote links aren't links: rustdoc's markdown parser doesn't do footnotes.

It's a common technique in plaintext to do footnotes with [0] [1], etc. There is no expectation that this will resolve because it's not a link -- the footnote itself contains text (not a URL).

[ollie27]

rustdoc's markdown parser doesn't do footnotes.

rustdoc does support footnotes. The syntax is [^0].

[Manishearth]

Oh, huh. TIL.

Still not sure if we should be warning about those (we don't warn about broken links either) but I guess it's fine.

[estebank]

Could we suggest using the footnote syntax when not resolving a link that is only a number?

[Manishearth]

Yeah, we could.

…

On Sat, Mar 9, 2019, 6:15 PM Esteban Kuber ***@***.***> wrote: Could we suggest using the footnote syntax when not resolving a link that is only a number? — You are receiving this because you authored the thread. Reply to this email directly, view it on GitHub <#59037 (comment)>, or mute the thread <https://github.com/notifications/unsubscribe-auth/ABivSK0v88pxWR9xu6kuviuK6ziakbJOks5vVGq4gaJpZM4bmfXr> .

[QuietMisdreavus]

Could we suggest using the footnote syntax when not resolving a link that is only a number?

Did we want to include this on this PR? If not, r=me, otherwise i'll wait to see it.

[Manishearth]

Nah, that would be a different lint I think, but feel free to add it yourself.

@bors r=QuietMisdreavus

[bors]

📌 Commit a4ea084 has been approved by QuietMisdreavus