Re: [PATCH] rust: clk: use the type-state pattern

[Daniel Almeida <daniel.almeida@collabora.com>]

> On 30 Jul 2025, at 10:27, Daniel Sedlak <daniel@sedlak.dev> wrote:
> 
> 
> On 7/30/25 2:59 PM, Daniel Almeida wrote:
>> […]
>>> We essentially would like to have a `#[sealed]` attribute that we can
>>> put on a trait to avoid the `mod private { pub trait Sealed }` dance.
>>> (so a trait that cannot be implemented outside of the module declaring
>>> it)
>>> 
>>> ---
>>> Cheers,
>>> Benno
>> This is not exactly what you said, but how about a declarative macro? e.g.:
>> macro_rules! sealed {
>>     ($($ty:ident),* $(,)?) => {
>>         mod private {
>>             pub trait Sealed {}
>>             $(impl Sealed for super::$ty {})*
>>         }
>>         use private::Sealed;
>>     };
>> }
>> sealed!(Unprepared, Prepared, Enabled)
>> Note that I am just brainstorming the general idea here, I did not test it yet.
> 
> I think that API-wise it would be better to have a proc-macro #[sealed], something similar to [1], as it may provide better error messages, when used incorrectly. So the outcome could look like.
> 
> #[sealed]
> pub trait ClkState {
> …
> }
> 
> And then
> 
> #[sealed]
> impl ClkState for XXX {
> …
> }
> 
> If you are interested, I can try to look into that.
> 
> Link: https://crates.io/crates/sealed [1]
> 
> Thanks!
> Daniel

If you have the bandwidth, that would be nice indeed! :)

— Daniel