{"ast_node_type":"other","tokens":[{"end":83,"kind":"keyword","start":0,"text":"a_is_expected:"}]}
            a_is_expected: false, // when coercing from `a` to `b`, `b` is expected
        let subtype_predicate = predicate.map_bound(|p| ty::SubtypePredicate {
            a: p.a,