Implement PartialEq between &str and OsString

[GabrielMajeri]

This fixes #49854.

It allows equality comparison between OsString values and str references, such as os_string == "something".

[rust-highfive]

Thanks for the pull request, and welcome! The Rust team is excited to review your changes, and you should hear from @bluss (or someone else) soon.

If any changes to this PR are deemed necessary, please add them as extra commits. This ensures that the reviewer can see what has changed since they last reviewed the code. Due to the way GitHub handles out-of-date commits, this should also make it reasonably obvious what issues have or haven't been addressed. Large or tricky changes may require several passes of review and changes.

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[rust-highfive]

The job x86_64-gnu-llvm-3.9 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:start:tidy
tidy check
[00:04:57] * 547 error codes
[00:04:57] * highest error code: E0911
[00:04:58] tidy error: /checkout/src/libstd/ffi/os_str.rs:420: mismatches to previous in: ["since"]
[00:04:58] tidy error: /checkout/src/libstd/ffi/os_str.rs:434: mismatches to previous in: ["since"]
[00:04:58] some tidy checks failed
[00:04:58] 
[00:04:58] 
[00:04:58] 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"
[00:04:58] 
[00:04:58] 
[00:04:58] failed to run: /checkout/obj/build/bootstrap/debug/bootstrap test src/tools/tidy
[00:04:58] Build completed unsuccessfully in 0:01:52
[00:04:58] Build completed unsuccessfully in 0:01:52
[00:04:58] Makefile:79: recipe for target 'tidy' failed
[00:04:58] make: *** [tidy] Error 1

The command "stamp sh -x -c "$RUN_SCRIPT"" exited with 2.
travis_time:start:03bf8b10
$ date && (curl -fs --head https://google.com | grep ^Date: | sed 's/Date: //g' || true)

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)

[GabrielMajeri]

Not sure which stability attributes would be right for this change.

[clarfonthey]

@GabrielMajeri what you have is fine, although you should change feature = "rust1" to something else, like feature = "os_str_str_ref_eq" or something like that

[pietroalbini]

Ping from triage @bluss! This PR needs your review.

[estebank]

Can you add a run-pass test for the feature?

[estebank]

@rust-lang/lang should this be instastable on 1.28? Other than that lgtm.

[nikomatsakis]

That's really a @rust-lang/libs decision, I think.

[nikomatsakis]

Was it formally decided elsewhere to add these impls? I don't see much discussion on #49854

[nikomatsakis]

I'm nominated for someone on @rust-lang/libs to render a decision of some kind.

[dtolnay]

We have all of the following:

// & <-> Owned are comparable
impl<'a> PartialEq<&'a str> for String
impl<'a> PartialEq<String> for &'a str

// utf8 <-> OS are comparable
impl PartialEq<str> for OsString
impl PartialEq<OsString> for str

So I believe it makes sense to provide these as well.

impl<'a> PartialEq<&'a str> for OsString
impl<'a> PartialEq<OsString> for &'a str

@rfcbot fcp merge

[rfcbot]

Team member @dtolnay has proposed to merge this. The next step is review by the rest of the tagged teams:

• @Kimundi
• @SimonSapin
• @alexcrichton
• @dtolnay
• @sfackler
• @withoutboats

No concerns currently listed.

Once a majority of reviewers approve (and none object), this will enter its final comment period. If you spot a major issue that hasn't been raised at any point in this process, please speak up!

See this document for info about what commands tagged team members can give me.

[rfcbot]

🔔 This is now entering its final comment period, as per the review above. 🔔

[rfcbot]

The final comment period, with a disposition to merge, as per the review above, is now complete.

[SimonSapin]

@bors r+

[bors]

📌 Commit 1e85cb3a595439e9f16163553725099e0c0da60f has been approved by SimonSapin

[bors]

🔒 Merge conflict

This pull request and the master branch diverged in a way that cannot be automatically merged. Please rebase on top of the latest master branch, and let the reviewer approve again.

How do I rebase?

Assuming self is your fork and upstream is this repository, you can resolve the conflict following these steps:

1. git checkout os-str-compare (switch to your branch)
2. git fetch upstream master (retrieve the latest master)
3. git rebase upstream/master -p (rebase on top of it)
4. Follow the on-screen instruction to resolve conflicts (check git status if you got lost).
5. git push self os-str-compare --force-with-lease (update this PR)

You may also read Git Rebasing to Resolve Conflicts by Drew Blessing for a short tutorial.

Please avoid the "Resolve conflicts" button on GitHub. It uses git merge instead of git rebase which makes the PR commit history more difficult to read.

Sometimes step 4 will complete without asking for resolution. This is usually due to difference between how Cargo.lock conflict is handled during merge and rebase. This is normal, and you should still perform step 5 to update this PR.

Error message

CONFLICT (file/directory): There is a directory with name src/libbacktrace in heads/homu-tmp. Adding src/libbacktrace as src/libbacktrace~HEAD
Automatic merge failed; fix conflicts and then commit the result.

[estebank]

@bors r=SimonSapin

[bors]

📌 Commit fbd3c92 has been approved by SimonSapin

[bors]

⌛ Testing commit fbd3c92 with merge 87ecf54...

[bors]

☀️ Test successful - status-appveyor, status-travis
Approved by: SimonSapin
Pushing 87ecf54 to master...