Cleanup: Use `declare_lint_pass!` and `impl_lint_pass!`

[Centril]

Introduced in rust-lang/rust#59669, macros declare_lint_pass! and impl_lint_pass! are added to librustc/lint/mod.rs. These should help to remove some boilerplate from clippy as well.

cc @oli-obk

[kraai]

I'm going to try to do this. I don't think these macros are available on nightly yet, so I'm building a new toolchain that I hope will include them.

[Centril]

The PR was merged and is in rust-lang/rust upstream :)

[oli-obk]

@kraai there's no need to build a toolchain. You can download even master toolchains via rustup by using our https://github.com/rust-lang/rust-clippy/blob/master/setup-toolchain.sh script

[kraai]

@oli-obk Thanks! I'm trying it now.

[kraai]

I tried using declare_lint_pass! for approx_const but it triggered lint_without_lint_pass. 8386ad2 contains the changes I tried. Is the change wrong or does lint_without_lint_pass need to be updated?

[flip1995]

It could be the case, that the lint_withou_lint_pass lint is unable to detect LintPasses declared by a macro. I will look into this tomorrow evening and get back to you!

[kraai]

@flip1995 Thanks!

[flip1995]

Yeah the lint was broken. You can find the fix here: flip1995/rust-clippy@87ab2e6. Just cherry-pick the commit onto your branch or copy the fix by hand :)

[kraai]

@flip1995 Thanks!

[kraai]

I've started working on this at https://github.com/kraai/rust-clippy/tree/declare_lint_pass.

[flip1995]

The current state of your branch looks good. Multiple PRs got merged yesterday/today and you should rebase on the master branch before making bigger changes.