{"ast_node_type":"variable","tokens":[{"end":66,"kind":"keyword","start":0,"text":"let"}]}
    let impl_m_hir_id = tcx.local_def_id_to_hir_id(impl_m_def_id);
    let return_span = tcx.hir_fn_decl_by_hir_id(impl_m_hir_id).unwrap().output.span();