{"ast_node_type":"variable","tokens":[{"end":81,"kind":"keyword","start":0,"text":"let"}]}
                let ty_param = Ty::new_param(tcx, ty_param.index, ty_param.name);
                let ty_param = gat_generics.param_at(*ty_idx, tcx);
                // Same for the region. In our example, 'a corresponds