manual_unsigned_abs

[owenthewizard]

What it does

Replace -{signed} as {unsigned} with {signed}.unsigned_abs()

Advantage

Clear and concise meaning & order of operations.
No panics or overflow (potentially).

Drawbacks

No response

Example

let n: isize = -42;
-n as usize

Could be written as:

let n: isize = -42;
n.unsigned_abs()

[samueltardieu]

The example works only because n is negative. Should n be positive, the result would not be the same at all.

If you are thinking about n.abs() as usize, this is already handled by the CAST_ABS_TO_UNSIGNED lint.

[owenthewizard]

The example works only because n is negative. Should n be positive, the result would not be the same at all.

If you are thinking about n.abs() as usize, this is already handled by the CAST_ABS_TO_UNSIGNED lint.

Yeah, I accidentally omitted it from my example but in my code I had this:

let n: isize = -42;
if n.is_negative() {
    -n as usize
}

[samueltardieu]

Others might disagree, but I feel this is very specific (-n as … following is_negative() or < 0 or <= 0). Do you have evidence of this happening in the wild? I couldn't find code with this pattern.

Or maybe we could include it in a more general lint manual_abs which would also detect the same thing without as ….