我想定义一个类似于

pub struct ArInt<const W: usize, const S: bool>
{
   iarr : [i32; {(W + 31 + (!S))/32}],
}

我得到一个编译错误：

--> src/ar_int.rs:7:27
  |
7 |     iarr : [i32; {(W + 31 + (!S))/32}],
  |                           ^ no implementation for `usize + bool`
  |
  = help: the trait `Add<bool>` is not implemented for `usize`
  = help: the following other types implement trait `Add<Rhs>`:
            <&'a usize as Add<usize>>
            <&usize as Add<&usize>>
            <usize as Add<&usize>>
            <usize as Add>

我做了如下修改

pub struct ArInt<const W: usize, const S: bool>
{
    iarr : [i32; {(W + 31 + (!S) as usize)/32}],
}

我仍然得到一个错误：

error: unconstrained generic constant
 --> src/ar_int.rs:7:12
  |
7 |     iarr : [i32; {(W + 31 + (!S) as usize)/32}],
  |            ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  |
  = help: try adding a `where` bound using this expression: `where [(); {(W + 31 + (!S) as usize)/32}]:`

有办法让它工作吗？
PS：我有#![feature(generic_const_exprs)]
谢谢

**更新：**如@Caesar所述，按照编译器给出的提示即可。

pub struct ArInt<const W: usize, const S: bool>
where [(); {(W + 31 + (!S) as usize)/32}]:
{
    iarr : [i32; {(W + 31 + (!S) as usize)/32}],
}

但谁能解释一下“where”这句话的意思？看起来很奇怪
谢谢