lint: add extra integer lints, and partially fix some code

[teor2345]

Motivation

I thought we might be able to add some lints for risky integer conversions in PR #3401. But it turns out that code is actually needed for now. (Until we do #2211.)

But I thought I should submit the lints that did work.

Solution

• add some integer and pointer clippy lints that pass on our code
• partially fix an integer calculation lint

Review

Anyone can review this Rust and lint code, it's not urgent or important.

Reviewer Checklist

• CI passes with new lints
• Existing tests pass

Follow Up Work

We might want to enable some of these other lints eventually, but it's a very low priority.

[codecov]

Codecov Report

Merging #3409 (6d650b7) into main (499ae89) will decrease coverage by 0.03%.
The diff coverage is 92.30%.

@@            Coverage Diff             @@
##             main    #3409      +/-   ##
==========================================
- Coverage   78.34%   78.30%   -0.04%     
==========================================
  Files         267      267              
  Lines       31526    31529       +3     
==========================================
- Hits        24698    24690       -8     
- Misses       6828     6839      +11     

[oxarbitrage]

I think this is great, not only added more lints for integers but also suggests how to add more. The more we can have is def better. I am unsure if we should open a ticket with that TODO list or if the code text is enough.

[teor2345]

I think this is great, not only added more lints for integers but also suggests how to add more. The more we can have is def better. I am unsure if we should open a ticket with that TODO list or if the code text is enough.

I don't think we will add any more lints any time soon.