{"ast_node_type":"variable","tokens":[{"end":49,"kind":"keyword","start":0,"text":"let"}]}
    let trait_m_fty = tcx.fn_sig(trait_m.def_id);
    let impl_m_fty = tcx.fn_sig(impl_m.def_id);
    let trait_number_args = trait_m_fty.skip_binder().inputs().skip_binder().len();