Remove feature from the list of well known check-cfg name

[Urgau]

This PR removes feature from the list of well known check-cfg.

This is done for multiple reasons:

• Cargo is the source of truth, rustc shouldn't have any knowledge of it
• It creates a conflict between Cargo and rustc when there are no features defined.
  In this case Cargo won't pass any --check-cfg for feature since no feature will ever be passed, but rustc by having in it's list adds a implicit cfg(feature, values(any())) which is completely wrong. Having any cfg feature is unexpected not allow any feature value.

While doing this, I took the opportunity to specialise the diagnostic a bit for the case above.

r? @petrochenkov

[petrochenkov]

@bors r+

[bors]

📌 Commit 3fda3ef has been approved by petrochenkov

It is now in the queue for this repository.

[petrochenkov]

I don't understand full implications of the Miri change though.
If it's not strictly necessary for this PR, then I'd suggest landing it separately with a review from qualified people.

[Urgau]

I don't understand full implications of the Miri change though. If it's not strictly necessary for this PR, then I'd suggest landing it separately with a review from qualified people.

It's unfortunately required, and the reason it is, is because of Cargo not passing RUSTFLAGS to proc-macro made the bootstrap tool create the RUSTC_HOST_FLAGS which force pass some flags to our rustc shim. Inside that environment variable are some --check-cfg flags that activates checking of cfgs but the way the standard library is build by Miri makes cargo-miri not use bootstrap and so neither -Zcheck-cfg nor our extra --check-cfg are passed making the build fail on all but the bootstrap cfg.

Ignoring RUSTC_HOST_FLAGS when we detect Miri is the easiest way I found to solve the issue.

[bors]

🔒 Merge conflict

This pull request and the master branch diverged in a way that cannot be automatically merged. Please rebase on top of the latest master branch, and let the reviewer approve again.

How do I rebase?

Assuming self is your fork and upstream is this repository, you can resolve the conflict following these steps:

1. git checkout check-cfg-cargo-feature (switch to your branch)
2. git fetch upstream master (retrieve the latest master)
3. git rebase upstream/master -p (rebase on top of it)
4. Follow the on-screen instruction to resolve conflicts (check git status if you got lost).
5. git push self check-cfg-cargo-feature --force-with-lease (update this PR)

You may also read Git Rebasing to Resolve Conflicts by Drew Blessing for a short tutorial.

Please avoid the "Resolve conflicts" button on GitHub. It uses git merge instead of git rebase which makes the PR commit history more difficult to read.

Sometimes step 4 will complete without asking for resolution. This is usually due to difference between how Cargo.lock conflict is handled during merge and rebase. This is normal, and you should still perform step 5 to update this PR.

Error message

Auto-merging tests/ui/check-cfg/exhaustive-names.exhaustive_names.stderr
Auto-merging tests/ui/check-cfg/exhaustive-names.empty_names.stderr
Auto-merging tests/ui/check-cfg/exhaustive-names-values.rs
Auto-merging tests/ui/check-cfg/exhaustive-names-values.empty_names_values.stderr
CONFLICT (content): Merge conflict in tests/ui/check-cfg/exhaustive-names-values.empty_names_values.stderr
Auto-merging tests/ui/check-cfg/exhaustive-names-values.empty_cfg.stderr
CONFLICT (content): Merge conflict in tests/ui/check-cfg/exhaustive-names-values.empty_cfg.stderr
Auto-merging compiler/rustc_session/src/config.rs
Auto-merging compiler/rustc_lint/src/context.rs
Automatic merge failed; fix conflicts and then commit the result.

[Urgau]

@rustbot ready

[petrochenkov]

@bors r+

[bors]

📌 Commit 54c122e has been approved by petrochenkov

It is now in the queue for this repository.

[bors]

⌛ Testing commit 54c122e with merge 855c683...

[bors]

☀️ Test successful - checks-actions
Approved by: petrochenkov
Pushing 855c683 to master...

[rust-timer]

Finished benchmarking commit (855c683): comparison URL.

Overall result: no relevant changes - no action needed

@rustbot label: -perf-regression

Instruction count

This benchmark run did not return any relevant results for this metric.

Max RSS (memory usage)

Results

This is a less reliable metric that may be of interest but was not used to determine the overall result at the top of this comment.

	mean	range	count
Regressions ❌ (primary)	-	-	0
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-0.8%	[-0.8%, -0.8%]	1
All ❌✅ (primary)	-	-	0

Cycles

Results

This is a less reliable metric that may be of interest but was not used to determine the overall result at the top of this comment.

	mean	range	count
Regressions ❌ (primary)	-	-	0
Regressions ❌ (secondary)	9.7%	[2.6%, 25.6%]	6
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	-	-	0

Binary size

This benchmark run did not return any relevant results for this metric.

Bootstrap: 676.862s -> 677.73s (0.13%)
Artifact size: 313.76 MiB -> 313.77 MiB (0.01%)