{"ast_node_type":"variable","tokens":[{"end":44,"kind":"keyword","start":0,"text":"let"}]}
    let high = fx.bcx.ins().bor(high, sign);
    let sign = fx.bcx.ins().band_imm(rhs_high, 0x8000_0000_0000_0000_u64 as i64);
    let res = fx.bcx.ins().iconcat(low, high);