{"ast_node_type":"variable","tokens":[{"end":62,"kind":"keyword","start":0,"text":"let"}]}
                let pos = trait_number_args.saturating_sub(1);
                let (trait_m_sig, _) = &tcx.hir_expect_trait_item(def_id).expect_fn();
                trait_m_sig.decl.inputs.get(pos).map(|arg| {