Not considering unnormalized candidates in method selection for params

[compiler-errors]

https://crater-reports.s3.amazonaws.com/pr-133502-13/try%233cddd79d4be3c8f1e937d09ca618d192abc69373/gh/cpecu.di-server/log.txt

fn execute<K, F, R>(q: F::Item) -> R
where
    F: Iterator<Item = R>,
    F::Item: Into<K>,
    R: Into<String>,
{
    q.into()
}

Right now F::Item: Into<K> + R: Into<String> doesn't stall F::Item: Into<?0>, which is later inferred to ?0 = R and uses the reflexive impl.