False positive for cast_sign_loss

[Luro02]

cargo clippy -V

clippy 0.0.212 (52cebb1 2019-10-15)

Example code

#![warn(clippy::cast_sign_loss)]

fn main() {
    let value = i64::min_value().checked_abs().unwrap_or(0) as u64;
    
    assert_eq!(value, 0);
}

Playground

Problem

Clippy does warn, that the sign could be lost implicitly, even though it is done explicitly with checked_abs, which either returns Some(positive i64) or None.

Expected behavior

Clippy should ignore this case.

[flip1995]

Easy extension of #4614

[phansch]

This should be fixed with #4883