Re: [PATCH 3/5] rust: vmstate: convert to use builder pattern

[Zhao Liu <zhao1.liu@intel.com>]

> +unsafe extern "C" fn vmstate_pre_load_cb<
> +    T,
> +    F: for<'a> FnCall<(&'a T,), Result<(), impl Into<Errno>>>,
> +>(
> +    opaque: *mut c_void,
> +) -> c_int {
> +    // SAFETY: assumes vmstate_struct! is used correctly
> +    let result = F::call((unsafe { &*(opaque.cast::<T>()) },));
> +    into_neg_errno(result)

Thanks! Now I see why you used io::ErrorKind.

> +}

...

> +    #[must_use]
> +    pub const fn pre_load<F: for<'a> FnCall<(&'a T,), Result<(), impl Into<Errno>>>>(
> +        mut self,
> +        _f: &F,
> +    ) -> Self {

Do we need to assert F is not ()?

const { assert!(F::IS_SOME) };

And I think all the other callbacks need to be checked as well.

> +        self.0.pre_load = Some(vmstate_pre_load_cb::<T, F>);
> +        self
> +    }

Thank you :-) ! And though it's a preview,

Reviewed-by: Zhao Liu <zhao1.liu@intel.com>