More general PartialEq implementation for Option

[tomjakubowski]

Currently, only the case where T == U is covered. Presumably this is because of derive limitations, since this impl is indeed derived in libcore.

I believe it should be possible and correct to provide the following impl:

impl<T, U> PartialEq<Option<U>> for Option<T> where T: PartialEq<U>, U: PartialEq<T> {
    fn eq(&self, rhs: &Option<U>) -> bool {
        match (self, rhs) {
            (&Some(ref lhs), &Some(ref rhs)) if lhs == rhs => true,
            (&None, &None) => true,
            _ => false
        }
    }
}

[Aatch]

Seems reasonable to me. Though I wonder if both T: PartialEq<U> and U: PartialEq<T> are necessary.

[tomjakubowski]

Seems reasonable to me. Though I wonder if both T: PartialEq and U: PartialEq are necessary.

Ahh yes, that was a little cuteness that snuck in. Shouldn't be necessary to have both.

[withoutboats]

👍 Are there any similar impls on Option or Result that could be made more general?

[huonw]

This is a subset of rust-lang/rust#20063, and has in fact had a failed attempt as part of that issue: rust-lang/rust#20063 (comment) .

[Centril]

Triage: No movement since 2015.