{"ast_node_type":"variable","tokens":[{"end":75,"kind":"keyword","start":0,"text":"let"}]}
    let trait_m_args = infcx.fresh_args_for_item(DUMMY_SP, trait_m.def_id);
    let trait_m_sig = tcx.fn_sig(trait_m.def_id).instantiate(tcx, trait_m_args);