Wrap dyn type with parentheses in suggestion

[long-long-float]

Close #120223

Fix wrong suggestion that is grammatically incorrect.
Specifically, I added parentheses to dyn types that need lifetime bound.

help: consider adding an explicit lifetime bound
  |
4 |     executor: impl FnOnce(T) -> (dyn Future<Output = ()>) + 'static,
  |                                 +                       +++++++++++

[rustbot]

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[long-long-float]

@fmease Could you review this PR? Thank you.

[fmease]

Sure, I plan on reviewing this later today. Sorry for taking a bit, I'm assigned to several PRs and I continuously work on PRs myself ^^'

[bors]

☔ The latest upstream changes (presumably #121549) made this pull request unmergeable. Please resolve the merge conflicts.

[fmease]

I'm sorry for leaving you hanging like that! I have a couple of suggestions for how to structure this a bit differently and some correctness things.

At the moment your changes only trigger in very few cases. I think we should generalize it to apply to more + XXX-style suggestions.

First and foremost, I would check the other 3 usage sites bounds_span_for_suggestion whether they could benefit from this, too (I even suggest you to merge bounds_span_for_suggestion_with_parentheses into it in one of my review comments). You could even consider grep'ing through tests/ui/ to check if there are any other incorrect consider adding an explicit lifetime bound suggestions.

In summary, I'm a fan of fixing the incorrect diagnostic suggestion but I'd like to make sure to tap the full potential.

[long-long-float]

@fmease Thank you for detailed review! I will fix them and check for more patterns in a couple of days.

[long-long-float]

I will fix testing failure at first.

[fmease]

@rustbot review

[long-long-float]

@fmease

First and foremost, I would check the other 3 usage sites bounds_span_for_suggestion whether they could benefit from this, too.

I checked them:

• compiler/rustc_hir_typeck/src/method/suggest.rs
  • tests/ui/suggestions/impl-trait-with-missing-trait-bounds-in-arg.rs
    • The impl Trait accepts impl Foo + Bar so we don't need parenthesis.
    • I think this suggestion is for type parameters (impl Trait in arguments), not dyn.
• compiler/rustc_middle/src/ty/diagnostics.rs
  • Same as above?
• compiler/rustc_trait_selection/src/traits/error_reporting/type_err_ctxt_ext.rs
  • ?Sized cannot be used in trait object types (dyn).

You could even consider grep'ing through tests/ui/ to check if there are any other incorrect consider adding an explicit lifetime bound suggestions.

I searched consider adding an explicit lifetime bound under tests/ui and couldn't find any incorrect suggestions.

I think incorrect suggestions which need parentheses happen with only dyn (I'm not familiar with Rust, so it may incorrect).

[fmease]

Thanks a lot!

First and foremost, I would check the other 3 usage sites bounds_span_for_suggestion whether they could benefit from this, too.

I could find an example for each usage site. Please make them use open_paren_sp as well, thanks! :)

After that, this PR should be good to go! One more thing, could you squash the commits into one (or fewer) commits?

[long-long-float]

@fmease
Thank you for reviewing! I fixed to use open_paren_sp in all sites, added tests, and squashed commits. Could you check them?

[long-long-float]

@rustbot ready

[fmease]

#120929 (comment)

CI still has errors, please fix them. If you have any questions regarding the failures, don't hesitate to reach out and ask them!

[long-long-float]

@fmease Thank you! All tests are passed.

[fmease]

@bors r+ rollup

[bors]

📌 Commit 31e581e has been approved by fmease

It is now in the queue for this repository.