分配的数字太大而无法在位字段未定义的行为中表示

I have the following code:

我有以下代码:

#include <stdio.h>
#include <stdint.h>

enum nums {
    ONE,
    TWO,
    TWENTY = 20
};

struct field {

    uint32_t something : 4;
    uint32_t rest : 28;
};

int main(void) {

    struct field f;
    f.something = TWENTY;
    return 0;
}
#include