I would very much appreciate if someone tell me what does ~ means in Rust. I have not yet came upon it in TRPL book but in std for example in Struct std::boxed::Box we see:

```
pub const fn new_in(x: T, alloc: A) -> Self
where
A: ~const Allocator + ~const Destruct,
{
let mut boxed = Self::new_uninit_in(alloc);
unsafe {
boxed.as_mut_ptr().write(x);
boxed.assume_init()
}
}
```

Thanks.