Add an allow attribute suggestion along with the implied by suggestion

[Urgau]

This PR adds an #[allow(...)] attribute hep suggestion along with the implied by suggestion:

  note: `-W dead-code` implied by `-W unused`
+ help: to override `-W unused` add `#[allow(dead_code)]`

This PR also adds the OnceHelp lint level (similar to OnceNote) to only put the help message one time, like the implied note.

Related to #114030

[rustbot]

r? @wesleywiser

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[rustbot]

Some changes occurred in src/tools/clippy

cc @rust-lang/clippy

[xFrednet]

Do we maybe want to suggest #[expect] instead, if the lint_reasons feature is enabled? See RFC 2383

This is just a biased suggestion since I've implemented that attribute and am currently trying to push the stabilization, so please ignore it if you don't agree.

---

Besides that suggestion, I really like this change 👍

[ojeda]

@xFrednet That sounds sensible and may be a better default than allow, though it may not always be the desired one.

For instance, in the "temporary/development allow" case, consider dead_code. One may be still experimenting with a few things, and thus calling a function or commenting the call from time to time. So the code may go between the dead and used code a few times. In this case, having the allow may be more pleasant. But others may still prefer to have to use expect, in order to avoid forgetting about it even if it requires a bit more work.

In the "committed/permanent allow" case, it is definitely nice to know when something is superfluous. Having said that, I wonder about supporting several toolchain versions. If the behavior of a lint changes, then one could have an expect that starts triggering in a new release, in which case they would need to change it to allow. This may be undesirable for projects that aim to be warning-free as much as possible. I guess it is not much of a concern for rustc lints, assuming they are more "stable" (in behavior) vs. Clippy ones or other custom ones a project may use.

Perhaps the best solution is to suggest both, and let users decide.

By the way, it may be even better/easier to already go for expect if the lint_reasons feature would be split in two features (in the tracking issue I see you said you would prefer not to, though).

[Urgau]

@wesleywiser still interested in reviewing this MR ?

[Urgau]

r? compiler

[bors]

💔 Test failed - checks-actions

[ehuss]

@bors retry

error decoding response body: operation timed out

Still investigating.

[rust-log-analyzer]

The job dist-x86_64-msvc failed! Check out the build log: (web) (plain)

Click to see the possible cause of the failure (guessed by this bot)

    0: error decoding response body: operation timed out
    1: operation timed out

Stack backtrace:
   0: backtrace::backtrace::dbghelp::trace
             at C:\Users\runneradmin\.cargo\registry\src\index.crates.io-6f17d22bba15001f\backtrace-0.3.69\src\backtrace\dbghelp.rs:98
             at C:\Users\runneradmin\.cargo\registry\src\index.crates.io-6f17d22bba15001f\backtrace-0.3.69\src\backtrace\mod.rs:66
             at C:\Users\runneradmin\.cargo\registry\src\index.crates.io-6f17d22bba15001f\backtrace-0.3.69\src\backtrace\mod.rs:66
   2: backtrace::backtrace::trace<anyhow::backtrace::capture::impl$4::create::closure_env$0>
             at C:\Users\runneradmin\.cargo\registry\src\index.crates.io-6f17d22bba15001f\backtrace-0.3.69\src\backtrace\mod.rs:53
   3: anyhow::backtrace::capture::Backtrace::create
             at C:\Users\runneradmin\.cargo\registry\src\index.crates.io-6f17d22bba15001f\anyhow-1.0.75\src\backtrace.rs:216
   4: anyhow::backtrace::capture::Backtrace::capture
             at C:\Users\runneradmin\.cargo\registry\src\index.crates.io-6f17d22bba15001f\anyhow-1.0.75\src\backtrace.rs:204
   5: anyhow::error::impl$1::from<reqwest::error::Error>
             at C:\Users\runneradmin\.cargo\registry\src\index.crates.io-6f17d22bba15001f\anyhow-1.0.75\src\error.rs:551
   6: opt_dist::environment::windows::impl$1::prepare_rustc_perf
             at /rustc/1119c18100c1d15eeb2b3e6af5356c54ff602c30/src\tools\opt-dist\src\environment\windows.rs:46
   7: opt_dist::execute_pipeline::closure$0
             at /rustc/1119c18100c1d15eeb2b3e6af5356c54ff602c30/src\tools\opt-dist\src\main.rs:37
   8: opt_dist::utils::with_log_group<opt_dist::execute_pipeline::closure_env$0,enum2$<core::result::Result<tuple$<>,anyhow::Error> > >
             at /rustc/1119c18100c1d15eeb2b3e6af5356c54ff602c30/src\tools\opt-dist\src\utils\mod.rs:65
             at /rustc/1119c18100c1d15eeb2b3e6af5356c54ff602c30/src\tools\opt-dist\src\main.rs:207
  10: core::ops::function::FnOnce::call_once
             at /rustc/680cdf8168a906b4ea80af673c64e4a16f77be57\library\core\src\ops\function.rs:250
             at /rustc/680cdf8168a906b4ea80af673c64e4a16f77be57\library\core\src\ops\function.rs:250
  11: std::sys_common::backtrace::__rust_begin_short_backtrace<enum2$<core::result::Result<tuple$<>,anyhow::Error> > (*)(),enum2$<core::result::Result<tuple$<>,anyhow::Error> > >
             at /rustc/680cdf8168a906b4ea80af673c64e4a16f77be57\library\std\src\sys_common\backtrace.rs:154
             at /rustc/680cdf8168a906b4ea80af673c64e4a16f77be57\library\std\src\rt.rs:166
  13: core::ops::function::FnOnce::call_once
             at /rustc/680cdf8168a906b4ea80af673c64e4a16f77be57\library\core\src\ops\function.rs:250
             at /rustc/680cdf8168a906b4ea80af673c64e4a16f77be57\library\core\src\ops\function.rs:250
  14: core::ops::function::FnOnce::call_once<std::rt::lang_start::closure_env$0<enum2$<core::result::Result<tuple$<>,anyhow::Error> > >,tuple$<> >
             at /rustc/680cdf8168a906b4ea80af673c64e4a16f77be57\library\std\src\rt.rs:166
             at /rustc/680cdf8168a906b4ea80af673c64e4a16f77be57/library\std\src\rt.rs:148
  16: std::panicking::try::do_call
             at /rustc/680cdf8168a906b4ea80af673c64e4a16f77be57/library\std\src\panicking.rs:524
  17: std::panicking::try

[bors]

⌛ Testing commit 9190e96 with merge dbbc2d0cfbf7328b301488f385be5df4efdfcb66...

[bors]

💔 Test failed - checks-actions

[rust-log-analyzer]

A job failed! Check out the build log: (web) (plain)

Click to see the possible cause of the failure (guessed by this bot)

Prepare workflow directory
Prepare all required actions
Getting action download info
Download action repository 'actions/checkout@v3' (SHA:f43a0e5ff2bd294095638e18286ca9a3d1956744)
##[error]Can't use 'tar -xzf' extract archive file: /home/runner/work/_actions/_temp_7af74abc-37f2-4759-9ff4-e6004d6e6700/d3c29ed9-89cc-4599-ab90-b3bc137ce4d5.tar.gz. return code: 2.

[ehuss]

@bors retry

GitHub checkout failed

[ehuss]

@bors p=101

[bors]

⌛ Testing commit 9190e96 with merge 04374cd...

[bors]

☀️ Test successful - checks-actions
Approved by: petrochenkov
Pushing 04374cd to master...

[rust-timer]

Finished benchmarking commit (04374cd): 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)	2.2%	[2.2%, 2.2%]	2
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-0.5%	[-0.5%, -0.5%]	1
Improvements ✅ (secondary)	-1.4%	[-1.4%, -1.4%]	1
All ❌✅ (primary)	1.3%	[-0.5%, 2.2%]	3

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)	-	-	0
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-3.5%	[-3.6%, -3.4%]	2
All ❌✅ (primary)	-	-	0

Binary size

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

Bootstrap: 629.118s -> 629.115s (-0.00%)
Artifact size: 316.16 MiB -> 316.11 MiB (-0.01%)

[carols10cents]

I am SO excited by this, you have no idea. Not having something to easily copy-paste, and needing to change hyphens to underscores, is one of the most annoying papercuts I hit with Clippy.

@Urgau know that I will be sending thoughts of thanks your way for YEARS to come every time I can copy-paste an allow from this message ❤️ ❤️ ❤️ ❤️ ❤️