Implementation of Signed::abs is not correct in regard to the doc

[gui1117]

doc is: https://github.com/rust-num/num-traits/blob/d394467906aab26065b5e518f4449aa982c6dcb1/src/sign.rs#L13-L14

but implementation is https://github.com/rust-num/num-traits/blob/d394467906aab26065b5e518f4449aa982c6dcb1/src/sign.rs#L48-L50

the implementation doesn't return MIN but actually panic with overflow, see:

fn abs(t: &i32) -> i32 {
    if t.is_negative() { -*t } else { *t }
}

fn main() {
    println!("{}", abs(&i32::min_value()))
}

[cuviper]

It's actually more nuanced than that, because in release mode overflow silently wraps. We should probably be forwarding this implementation to std anyway, and the docs there explain:

The absolute value of i32::min_value() cannot be represented as an i32, and attempting to calculate it will cause an overflow. This means that code in debug mode will trigger a panic on this case and optimized code will return i32::min_value() without a panic.