Stabilize Path::try_exists() and improve doc

[Kixunil]

This stabilizes the Path::try_exists() method which returns
Result<bool, io::Error> instead of bool allowing handling of errors
unrelated to the file not existing. (e.g permission errors)

Along with the stabilization it also:

• Warns that the exists() method is error-prone and suggests to use
  the newly stabilized one.
• Suggests it instead of metadata() to handle errors.
• Mentions TOCTOU bugs to avoid false assumption that try_exists() is
  completely safe fixed version of exists().
• Renames the feature of still-unstable std::fs::try_exists() to
  fs_try_exists to avoid name conflict.

The tracking issue #83186 remains open to track fs_try_exists.

[rust-highfive]

Hey! It looks like you've submitted a new PR for the library teams!

If this PR contains changes to any rust-lang/rust public library APIs then please comment with @rustbot label +T-libs-api -T-libs to tag it appropriately. If this PR contains changes to any unstable APIs please edit the PR description to add a link to the relevant API Change Proposal or create one if you haven't already. If you're unsure where your change falls no worries, just leave it as is and the reviewer will take a look and make a decision to forward on if necessary.

Examples of T-libs-api changes:

• Stabilizing library features
• Introducing insta-stable changes such as new implementations of existing stable traits on existing stable types
• Introducing new or changing existing unstable library APIs (excluding permanently unstable features / features without a tracking issue)
• Changing public documentation in ways that create new stability guarantees
• Changing observable runtime behavior of library APIs

[rust-highfive]

r? @m-ou-se

(rust-highfive has picked a reviewer for you, use r? to override)

[Kixunil]

@rustbot label +T-libs-api -T-libs

[m-ou-se]

@rfcbot merge

[rfcbot]

Team member @m-ou-se has proposed to merge this. The next step is review by the rest of the tagged team members:

• @Amanieu
• @BurntSushi
• @dtolnay
• @joshtriplett
• @m-ou-se
• @yaahc

No concerns currently listed.

Once a majority of reviewers approve (and at most 2 approvals are outstanding), 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.

[Kixunil]

Hmm:

tidy error: binary checked into source: /checkout/compiler/rustc_error_messages/src/lib.rs

I don't understand this. git show HEAD doesn't show anything binary that I had accidentally added. Can someone help, please?

[klensy]

Looks like you changed metadata of file, like chmod ..., revert it.

rust/src/tools/tidy/src/bins.rs

Lines 37 to 39 in be16c61

	fn is_executable(path: &Path) -> std::io::Result<bool> {
	Ok(path.metadata()?.mode() & 0o111 != 0)
	}

Yes, you can see file permissions change in git diff or in github diff compiler/rustc_error_messages/src/lib.rs

[Kixunil]

@klensy thanks! (I have a vim script that sets executable bit for files beginning with #!. :))

[rfcbot]

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

[bors]

☔ The latest upstream changes (presumably #98091) made this pull request unmergeable. Please resolve the merge conflicts.

[rfcbot]

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

As the automated representative of the governance process, I would like to thank the author for their work and everyone else who contributed.

This will be merged soon.

[dtolnay]

@bors r+

[bors]

📌 Commit 5608707 has been approved by dtolnay

[bors]

⌛ Testing commit 5608707 with merge 17c6bde...