{"ast_node_type":"variable","tokens":[{"end":99,"kind":"keyword","start":0,"text":"let"}]}
                let ref_arg = ctx.arena.alloc(ctx.expr_ref(arg.span.with_ctxt(macsp.ctxt()), arg));
                let arg = ctx.lower_expr(&arg.expr);
                make_argument(ctx, placeholder_span, ref_arg, ty)