cast_possible_truncation: Fix some false-positive cases

[tesuji]

Fix partially #7486 (comment).
Fix #9613.
changelog: [cast_possible_truncation]: fix some false-positive on % operator, valid constants, and size_of

[rustbot]

r? @Jarcho

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[xFrednet]

Hey, this is a ping from triage. @Jarcho can you give this PR a review? It's totally fine if you don't have the time right now, you can reassign the PR to a random team member using r? clippy.

@rustbot ready

[Jarcho]

Looks ok. Thank you @bors r+

[bors]

📌 Commit 3770c8f has been approved by Jarcho

It is now in the queue for this repository.

[bors]

⌛ Testing commit 3770c8f with merge 436f9ee...

[bors]

💔 Test failed - checks-action_test

[Jarcho]

@tesuji you may need to rebase to fix the errors.

[tesuji]

I think I'm stuck. I don't know any ways to bless test for 32-bit target. Running with cargo uibless --target i686-unknown-linux-gnu fail with error says that compiletest doesn't recognize --target option. Could you me give any pointers to workaround this?

[Jarcho]

The uibless command is defined in .cargo/config.toml as test --test compile-test -- -- --bless. You can edit that as needed.

[tesuji]

It's complicated than I expected:

> rustup install nightly-2024-07-25-i686-unknown-linux-gnu -c rust-src rustc-dev llvm-tools-preview
> # also install i386 zlib
> cargo +i686-unknown-linux-gnu uitest

But hey, since I added this condition to_nbits < from_nbits && to_nbits <= 32, on line 137, the diff will be different
between 32-bti and 64-bit targets. How do I mark this with compiletest?

[Jarcho]

That condition should be to_nbits <= from_nbits || to_nbits <= 32. We always want to lint usize to u32 casts as they're not portable.

[tesuji]

If the constant is locally defined and have value < u32::MAX, it will be linted again when changes the condition.

I don't have time or enough motivation for developing clippy in general. Closing this for now.

Anyway, thank you very much for your reviewing, Jarcho.