Re: [PATCH 03/12] rust: callbacks: allow passing optional callbacks as ()

[Zhao Liu]

On Fri, Feb 07, 2025 at 11:16:14AM +0100, Paolo Bonzini wrote:
> Date: Fri,  7 Feb 2025 11:16:14 +0100
> From: Paolo Bonzini <pbonzini@redhat.com>
> Subject: [PATCH 03/12] rust: callbacks: allow passing optional callbacks as
>  ()
> X-Mailer: git-send-email 2.48.1
> 
> In some cases, callbacks are optional.  Using "Some(function)" and "None"
> does not work well, because when someone writes "None" the compiler does
> not know what to use for "F" in "Option<F>".
> 
> Therefore, adopt () to mean a "null" callback.  It is possible to enforce
> that a callback is valid by adding a "let _: () = F::ASSERT_IS_SOME" before
> the invocation of F::call.
> 
> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
> ---
>  rust/qemu-api/src/callbacks.rs | 97 ++++++++++++++++++++++++++++++++++
>  1 file changed, 97 insertions(+)
>

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