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

[Daniel Sedlak]

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