{"ast_node_type":"variable","tokens":[{"end":79,"kind":"keyword","start":0,"text":"let"}]}
                let sig = self.tcx.fn_sig(assoc.def_id).instantiate_identity();
                // but for CandidateSource::Trait, `Self` is still `Self`
                sig.inputs().skip_binder().get(0).and_then(|first| {