Downgrade interior_mutable_const lints to warn by default

[longlb]

This change updates the two lints in the file non_copy_const.rs to be warn by default rather than deny by default. It also updates the known problems for declare_interior_mutable_const to mention some issues that are affected by the lints.

fixes #5863
changelog: none

[rust-highfive]

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[yaahc]

Hi @longlb, ty for the PR. I'm a little confused by the changes in it though. Are the unnecessary_sort_by changes related to #5863? Looking at this it seems like you might have also gone and fixed #6001 and accidentally combined the changes for both fixes into one PR.

Another thing, do we have any ui tests for interior _mutable_const? I'd have expected a stderr file to get updated with some of the text of the error message shifting from error to warn, but I don't see that in this PR. If it's because we're missing a test could we add some basic ones that generate the warning just so we can verify that it is warning and at the correct level?

[longlb]

Hi @yaahc. Regarding the unnecessary_sort_by changes, I did not make them. I pulled them from the main repository when I saw that someone else had commit to it, but I did not check what they were since they did not create a conflict. They are the changes that were recently merged to resolve issue #6006, so I think that removing them from my PR should be okay.

For the UI tests, both interior_mutable_constant lints have some. The stderr files didn't update because I thought it would happen automatically, so that's my mistake. I'll fix it.

[longlb]

Is there a way to see all the errors or warnings that clippy produces on the tests? I've been trying to see how changing between warn and error change the output, but I can't see the output anywhere since both pass all the given tests.

[rail-rain]

Hello @longlb. You can probably use CLIPPY_TESTS=true cargo run --bin clippy-driver -- -L ./target/debug on the test files directly although the fact that the test suite including CI is clear means the output hasn't changed by this lint level change. I think the cause of this quirk is the two test files have #![warn(borrow_interior_mutable_const)] and #![warn(declare_interior_mutable_const)] attributes for some reason. I'm not sure why these are there. The uitest should work without those.

[ebroto]

@longlb to get rid of all commits that are unrelated (and the last revert), you should do an interactive rebase on top of master, keeping only your commits.

This comment may be of help.

[longlb]

I messed up a bit while trying to fix the git stuff and wiped out my commits. I'll rewrite and open a new pull request when I'm done.