Add CodeFix::apply_solution and impl Clone

[Alexendoo]

What does this PR try to resolve?

In Clippy we have a good few lints that produce mutually exclusive suggestions e.g.

error: octal-looking escape in a literal
  --> tests/ui/octal_escapes.rs:6:19
   |
LL |     let _bad2 = b"\033[0m";
   |                   ^^^^
   |
help: if an octal escape is intended, use a hex escape instead
   |
LL |     let _bad2 = b"\x1b[0m";
   |                   ~~~~
help: if a null escape is intended, disambiguate using
   |
LL |     let _bad2 = b"\x0033[0m";
   |                   ~~~~~~

For these we have to disable rustfix tests since the suggestions are overlapping, this PR adds a method to rustfix that ui_test could use in order to produce multiple .fixed files, one for each alternative suggestion

Additional information

It does not work for for multiple suggestions coming from a single subdiagnostic (Diag::span_suggestions) e.g.

help: consider importing one of these items
  |
1 + use std::collections::HashMap;
  |
1 + use ahash::HashMap;

Solving this would be blocked on rust-lang/rust#53934, on the Clippy side we only have one use of span_suggestions however so it's still very useful without this

The test cases use Clippy lints that I generated by setting the parse_and_replace test to use clippy-driver because of familiarity, if there's a rustc case that does multiple suggestions it would be good to go with that

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[Alexendoo]

Ah I misread how the test suite worked, thought it only ran rustc on bless so I'll need to find some rustc examples that produce multiple suggestions

[weihanglo]

Thanks for the pull request. I saw you've changed the test snapshot to rustc diagnostics. Would you mind

• Providing issue links and code in Clippy of where Clippy disables rustfix tests.
• Sharing the Clippy diagnositc JSON which rustfix is not happy with.
• Also how Clippy is going to use that new public interface so we won't mess up stuff in the future.

That would make the intent clear and connected. Thank you!

[weihanglo]

Do we consider duplicate solutions inside a suggestion? We should only apply once in that situation. See #13728.
That said, it can be considered a rustc bug and we do nothing here if the only consumer is clippy.

[Alexendoo]

I don't think we have an issue open for it but here's a few test examples with disabled rustfix due to having multiple suggestions

• https://github.com/rust-lang/rust-clippy/blob/29cc5c691c574b54b2fcfed51c22f8bb51110919/tests/ui/assign_ops2.rs#L1
• https://github.com/rust-lang/rust-clippy/blob/29cc5c691c574b54b2fcfed51c22f8bb51110919/tests/ui/borrow_deref_ref_unfixable.rs#L1
• https://github.com/rust-lang/rust-clippy/blob/29cc5c691c574b54b2fcfed51c22f8bb51110919/tests/ui/join_absolute_paths.rs#L1

https://github.com/rust-lang/cargo/blob/50fa303d5c3e61c95e1a87b5b12ef3de19d415db/crates/rustfix/tests/separate/separate.json is a good Clippy diagnostic example

The plan would be to add support to ui_test that Clippy uses for its tests, similar to the added tests here there would be multiple fixed files when suggestions contain multiple solutions

I just noticed though that since the fields of Suggestion are pub this could be done without an API change to rustfix. Do you think this should live in rustfix or be implemented outside? The Clone/apply_solution additions for CodeFix would still be useful if it's implemented outside

[weihanglo]

Thanks for the information! Now I can clearly see where it came from :)

I just noticed though that since the fields of Suggestion are pub this could be done without an API change to rustfix. Do you think this should live in rustfix or be implemented outside?

Sounds that it's better being done on Clippy/ui_test side if it is the only consumer. It also reduces cross repo works if something needs to change in the futre.

The Clone/apply_solution additions for CodeFix would still be useful if it's implemented outside

Yeah I am good with these additions.

[Alexendoo]

A much smaller PR now 😄

[weihanglo]

Thanks!

@bors+

BTW, do you know what rust-cloud-vms is? I saw it force-pushed code you commited. Or, are you a bot?

[Alexendoo]

🤖

It's because I pushed from one of the dev desktops, they have a funky credential helper setup going on that I guess appears as though it's coming from the bot

[weihanglo]

@bors r+

[bors]

📌 Commit 5a15397 has been approved by weihanglo

It is now in the queue for this repository.

[bors]

⌛ Testing commit 5a15397 with merge 99361c4...

[bors]

☀️ Test successful - checks-actions
Approved by: weihanglo
Pushing 99361c4 to master...