<int>.signum() can be safely cast to any signed integer

[jhpratt]

clippy version: clippy 0.0.212 (4ee1206 2020-02-01)

<int>.signum() always returns -1, 0, or 1. As such, it can safely be cast to any signed integer.

The following currently triggers clippy::cast_possible_truncation, but there's no reason it needs to.

let x: i64 = 5;
let _ = x.signum() as i32;

Related: #4605, #4818

[spaihippo]

Hi, if it's ok, I would like to give this a try as my first issue.

[flip1995]

Awesome. There were previous PRs, that addressed similar issues linked above. You can use them for inspiration. To get familiar with testing in Clippy (and Clippy hacking in general) you can take a look at this document: https://github.com/rust-lang/rust-clippy/blob/master/doc/adding_lints.md#testing

[spaihippo]

Thanks! I'll take a look at those.

[brightly-salty]

I can attempt to implement this and submit a PR if @s00kee isn't still working on it.