Limit the `[identity_op]` lint to integral operands.

[alex-ozdemir]

changelog: limit [`identity_op`] to integral operands

In the [`identity_op`] lint, if the operands are non-integers, then the lint is likely
wrong.

[rust-highfive]

Thanks for the pull request, and welcome! The Rust team is excited to review your changes, and you should hear from @camsteffen (or someone else) soon.

Please see the contribution instructions for more information.

[camsteffen]

Do you have an example false positive that this fixes?

[alex-ozdemir]

Ah yes. good_lp overloads the shift operators to construct bounds in an ILP. See, for example this overload.

I encountered the false positive here.

[camsteffen]

I see. Can you add a test for that?

Also I think you should use peel_refs().is_integral() since there can be + &0.

[alex-ozdemir]

Good suggestions.

First commit avoids ignoring refs.

Second commit actually catches x << &0, by peeling refs around constants.

[camsteffen]

Thanks!

@bors r+

[bors]

📌 Commit ee6d5c5 has been approved by camsteffen

[bors]

⌛ Testing commit ee6d5c5 with merge 16ef044...

[bors]

☀️ Test successful - checks-action_dev_test, checks-action_remark_test, checks-action_test
Approved by: camsteffen
Pushing 16ef044 to master...