Add check for assert_eq macros to unit_cmp lint

[Lythenas]

changelog: Add check for unit comparisons through assert_eq!, debug_assert_eq!, assert_ne! and debug_assert_ne! macros to unit_cmp lint.

fixes #4481

[flip1995]

Thanks, only a NIT.

[Lythenas]

Is it fine to use () as arguments in the tests? Or should I use blocks like with ==?

Should I also update the description of the lint to say it applies to asserts too?

[flip1995]

An update of the description of the lint would be good. And adding more tests is never wrong :)

[Lythenas]

Ok I will make changes to the description and the test. Also I just realized simply applying your suggestion through the github interface wasn't enough because I also need to update the .stderr 🤦‍♂️

[Lythenas]

Is there a way to preview the updated lint documentation?

[flip1995]

Is there a way to preview the updated lint documentation?

Kind of, but this isn't really necessary. But since you asked:

1. You can export the lint documentation with the ./util/export.py script.
2. After that you can open ./util/gh-pages/index.html with firefox or another browser
3. (If you're using firefox >= 68.0 you have to set privacy.file_unique_origin in about:config to false before the page can be displayed. See: https://developer.mozilla.org/en-US/docs/Web/HTTP/CORS/Errors/CORSRequestNotHttp; other browsers may also have the same "problem", but I didn't look into how to fix it in other browsers 😉)

[Lythenas]

@flip1995 I think I'm done. Can you check if my changes to the doc is ok?

[flip1995]

Looks great, thank you!

@bors r+

[bors]

📌 Commit 5a0a2b3 has been approved by flip1995

[bors]

⌛ Testing commit 5a0a2b3 with merge 54bf4ff...

[bors]

☀️ Test successful - checks-travis, status-appveyor
Approved by: flip1995
Pushing 54bf4ff to master...