`client_side_validation` regression

[compiler-errors]

https://crater-reports.s3.amazonaws.com/pr-133502-13/try%233cddd79d4be3c8f1e937d09ca618d192abc69373/gh/cyphernet-dao.ssi/log.txt

struct Holder<T>(T);

impl<T> Holder<T> {
    fn as_type(&self) -> &T {
        &self.0
    }
}

trait CommitEncode {
    fn commit_encode(&self);
}

impl<T: 'static> CommitEncode for Holder<&'static T>
where
    T: CommitEncode,
{
    fn commit_encode(&self) {
        self.as_type().commit_encode();
    }
}

impl<T: 'static> CommitEncode for T
where
    T: Other,
    Holder<&'static T>: CommitEncode,
{
    fn commit_encode(&self) {
        todo!()
    }
}

trait Other {}
impl<T> Other for &T {}

fn main() {}

[compiler-errors]

Method selection in the old solver is treating the overflowing goal as a hard error, I think.

[compiler-errors]

The cycle here is, when doing method probing for &T: CommitEncode -> Holder<&&T>: CommitEncode -> &T: CommitEncode.

Old solver treats the cycle as fatal and disqualifies that method candidate, then trying the autoderef'd version which would need to satisfy T: CommitEncode which is satisfied via a param-env candidate.

[lcnr]

The cycle here is, when doing method probing for &T: CommitEncode -> Holder<&&T>: CommitEncode -> &T: CommitEncode.

Old solver treats the cycle as fatal and disqualifies that method candidate, then trying the autoderef'd version which would need to satisfy T: CommitEncode which is satisfied via a param-env candidate.

the old solver still has fatal cycle handling? :o

[compiler-errors]

Yes, on process_backedge in fulfill unfortunately lol

[lcnr]

slightly simplier for me to understand it

struct Holder<T>(T);
trait CommitEncode {
    fn commit_encode(self);
}

impl<T: 'static> CommitEncode for Holder<&'static T>
where
    T: CommitEncode + Copy,
{
    fn commit_encode(self) {
        let x = &self.0;
        x.commit_encode();
    }
}

impl<T: 'static> CommitEncode for T
where
    T: NotHolder,
    Holder<&'static T>: CommitEncode,
{
    fn commit_encode(self) {
        todo!()
    }
}

trait NotHolder {}
impl<T> NotHolder for &T {}

fn main() {}