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improve error message when a cfg-ed out item is resolved#154037

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scrabsha wants to merge 1 commit intorust-lang:mainfrom
scrabsha:push-ltqusupltwzm
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improve error message when a cfg-ed out item is resolved#154037
scrabsha wants to merge 1 commit intorust-lang:mainfrom
scrabsha:push-ltqusupltwzm

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@scrabsha scrabsha commented Mar 18, 2026 •
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the current note for "cannot find function f in this scope" is:

note: found an item that was configured out
 --> src/main.rs:4:4
  |
3 | #[cfg(foo = "bar")]
  |       ----------- the item is gated behind the `bar` feature
4 | fn f() {}
  |    ^

i think mentioning only bar in the label is misleading. in more complicated setups, this leads to obscure notes such as "the item is gated behind the ptr feature".

this PR improves the situation by naming both the name and value in the label (in the example i linked, target_has_atomic and ptr). while i was at it, i also special-cased #[cfg(false)], #[cfg(any())] and #[cfg(feature = "meow")] (aka Cargo features).

i also tried to use #[derive(SubDiagnostic)] on FoundItemConfigureOut, with no success (the resulting diagnostic was showing multiple help snippets, i couldn't figure out how to merge them). any help would be appreciated.

r? you Esteban, as you added the diagnostic initially - feel free to unassign yourself if necessary :)

r? @estebank

nevermind apparently that's not possible --'

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rustbot commented Mar 18, 2026

Failed to set assignee to you: invalid assignee

Note: Only org members with at least the repository "read" role, users with write permissions, or people who have commented on the PR may be assigned.

@rustbot rustbot added S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. T-compiler Relevant to the compiler team, which will review and decide on the PR/issue. labels Mar 18, 2026
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rustbot commented Mar 18, 2026

Failed to set assignee to estebank~~: invalid assignee

Note: Only org members with at least the repository "read" role, users with write permissions, or people who have commented on the PR may be assigned.

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scrabsha commented Mar 18, 2026

@rustbot reroll

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Kivooeo commented Mar 18, 2026

nevermind apparently that's not possible

r? estebank

@rustbot rustbot assigned estebank and unassigned petrochenkov Mar 18, 2026
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scrabsha commented Mar 18, 2026 •
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@Kivooeo if you don't mind me asking, why did it fail when i opened the PR? i remember r?ing people in the past, i'm a bit confused :/

edit: oah i did not suspect this would trigger rustbot again, sorry for the noise

edit: i think this is because rustbot looks for the first occurrence of r question mark anywhere in the message and tries to use that (i thought it had to be at the beginning of a line).

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rustbot commented Mar 18, 2026

Failed to set assignee to ing: invalid assignee

Note: Only org members with at least the repository "read" role, users with write permissions, or people who have commented on the PR may be assigned.

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jdonszelmann commented Mar 18, 2026

Might be good to also special case any(), the old way of writing false

@scrabsha scrabsha force-pushed the push-ltqusupltwzm branch from d07ece2 to 995f854 Compare March 18, 2026 10:28
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scrabsha commented Mar 18, 2026

done, thanks!

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Kivooeo commented Mar 18, 2026

@Kivooeo if you don't mind me asking, why did it fail when i opened the PR? i remember r?ing people in the past, i'm a bit confused :/

The issue is that the r-? command assigns the reviewer based on the word that follows it. In your first attempt, you wrote "r-? you Esteban" -- but "you" isn't a valid reviewer. Then you tried "estebank~~", which is also incorrect

To assign a reviewer correctly, you need to use their exact GitHub username. In this case, it should be "estebank"

jdonszelmann
jdonszelmann reviewed Apr 20, 2026
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Comment thread tests/ui/cfg/diagnostics-same-crate.rs
}

#[cfg(i_dont_exist_and_you_can_do_nothing_about_it)] //~ NOTE the item is gated here
#[cfg(i_dont_exist_and_you_can_do_nothing_about_it)] //~ NOTE the item is gated behind `i_dont_exist_and_you_can_do_nothing_about_it`
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@jdonszelmann jdonszelmann Apr 20, 2026 •
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--cfg i_dont_exist_and_you_can_do_nothing_about_it does do something about it :3

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jdonszelmann
jdonszelmann reviewed Apr 20, 2026
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Comment thread compiler/rustc_resolve/src/diagnostics.rs Outdated
@rustbot rustbot added S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. and removed S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. labels Apr 20, 2026
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rustbot commented Apr 20, 2026

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

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@scrabsha scrabsha force-pushed the push-ltqusupltwzm branch from 995f854 to 2a0f969 Compare April 23, 2026 17:12
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rustbot commented Apr 23, 2026

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.

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scrabsha commented Apr 23, 2026 •
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latest push contains:

@rustbot ready

@rustbot rustbot added S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. and removed S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. labels Apr 23, 2026
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