fn find_best_leaf_obligation<'db>(
infcx: &InferCtxt<'db>,
obligation: &Obligation<'db, Predicate<'db>>,
consider_ambiguities: bool,
) -> (Obligation<'db, Predicate<'db>>, Vec<Predicate<'db>>)fn find_best_leaf_obligation<'db>(
infcx: &InferCtxt<'db>,
obligation: &Obligation<'db, Predicate<'db>>,
consider_ambiguities: bool,
) -> (Obligation<'db, Predicate<'db>>, Vec<Predicate<'db>>)