use of round/floor/ceil on known integer value

[llogiq]

E.g. ceil(1f32)

[Manishearth]

FWIW I don't think we'll have too many issues with constants -- I think programmers will be smart enough to not do stuff like this (but footguns like the other issues on this repo would be harder to catch manually)

Still, I don't mind having stuff like this here.

[llogiq]

I just nicked it from FindBugs. And yes, I don't think it should be high priority.

[ThomasdenH]

What should this lint catch? For example, using std::f64::consts::PI.ceil() would be optimized by the compiler anyway and has more explanatory value than 4.

[alekhrycaiko]

Happy to jump in and take this 🎈

[alekhrycaiko]

From what I can see, ceil(1f32) is not a valid way of calling ceil currently.

ceil() exists on float types (e.g. f64 and f32) and would be caught by the Rust compiler if called on an int type. I'm not certain there's actually anything to catch here for reasons also brought up by @ThomasdenH

Is there some more specific requirements for what this lint should catch @llogiq

If not, perhaps this issue be closed?

[ThomasdenH]

Perhaps this lint is just for cases where the operation doesn't change the value?

[Manishearth]

From what I can see, ceil(1f32) is not a valid way of calling ceil currently.

Yes, that was pseudocode

This lint is about calling ceil on a known integer float value. So something like 1f32.ceil(). But as I mentioned earlier this seems pretty hard to do by accident.

[botahamec]

@rustbot claim
I've been looking at this for practice, and I'd like to try it. I got it to work with literals. I'm gonna try to see it I can figure out how to make it work with constants and if variables are possible. Could somebody let me know if I'm on a goose chase?

[xFrednet]

For constants you can take a look at clippy_utils::consts. However, I could see some use cases for calling these functions on constant values. Therefore, I think it might be better to only lint literals in code 🙃

I've you're stuck on an implementation detail, feel free to reach out or create a draft PR 🙃

[botahamec]

However, I could see some use cases for calling these functions on constant values. Therefore, I think it might be better to only lint literals in code 🙃

@xFrednet I think that's good point. I'll start working on a PR today