Improve invalid cfg predicate error

[evavh]

I have improved the error that is emitted when a non-existant cfg attribute is used. I removed the InvalidPredicate diagnostic, which does not provide much information, and used the function expected_specific_argument instead. This provides a nice link to the documentation. I have also blessed and updated the ui tests that broke because of this change.

Before:

error[E0537]: invalid predicate `does_not_exist`
 --> bad_error.rs:2:7
  |
2 | #[cfg(does_not_exist())]
  |       ^^^^^^^^^^^^^^^^

error: aborting due to 1 previous error

After:

error[E0539]: malformed `cfg` attribute input
 --> bad_error.rs:2:1
  |
2 | #[cfg(does_not_exist())]
  | ^^^^^^----------------^^
  |       |
  |       valid arguments are `any`, `all`, `not`, `target` or `version`
  |
  = note: for more information, visit <https://doc.rust-lang.org/reference/conditional-compilation.html#the-cfg-attribute>
help: must be of the form
  |
2 - #[cfg(does_not_exist())]
2 + #[cfg(predicate)]
  |

r? @JonathanBrouwer

[rustbot]

Some changes occurred in compiler/rustc_attr_parsing

cc @jdonszelmann, @JonathanBrouwer

[rustbot]

Thanks for the pull request, and welcome! The Rust team is excited to review your changes, and you should hear from @JonathanBrouwer (or someone else) some time within the next two weeks.

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[JonathanBrouwer]

Hmmm, "version" is an unstable predicate, could you only mention it if the corresponding feature gate is enabled?

View changes since the review

[rustbot]

Reminder, once the PR becomes ready for a review, use @rustbot ready.

[JonathanBrouwer]

Other than that it seems good, thanks a lot for the improvement!

[evavh]

I added the feature check! It seems one of the tests failed last time, I'm not sure why.

@rustbot ready

[JonathanBrouwer]

@evavh The change looks good, thanks!
The test that is failing is from the error-code index, you can reproduce this with ./x test error-index.
You need to remove the expected E0537 code from the example in the md.

[rustbot]

This PR was rebased onto a different main commit. Here's a range-diff highlighting what actually changed.

Rebasing is a normal part of keeping PRs up to date, so no action is needed—this note is just to help reviewers.

[JonathanBrouwer]

@bors r+ rollup
Thanks a lot! <3

View changes since this review

[rust-bors]

📌 Commit 851ab7a has been approved by JonathanBrouwer

It is now in the queue for this repository.