Implement {Signal,SignallingRef}#mapK

[rahulrangers]

Previously, calling .mapK on a SignallingRef[F, A] would yield a plain Ref[G, A], causing the extra signaling behavior (such as discrete, continuous) to be lost. This PR introduces a new helper class, TransformedSignallingRef, which implements mapK for SignallingRef so that all signal-specific operations are lifted to the new effect type. This change ensures that after a transformation, the resulting reference remains a full SignallingRef[G, A] with its intended functionality.

[rahulrangers]

@armanbilge Could you please review this and let me know if there are any mistakes that need correction?

[rahulrangers]

I think we can convert waitUntil with the transformed discrete and can you give me any idea like how can i try to override getAndDiscreteUpdates @armanbilge

[rahulrangers]

I'm encountering an issue while implementing the waitUntil method in the TransformedSignallingRef class. Specifically, the compiler raises an error indicating that it cannot find an implicit value for the parameter F: cats.effect.kernel.Concurrent[F].

[armanbilge]

Great, thanks, this looks good!

One final thing, can we add a test? Mostly I'm interested in a test to check that SignallingRef#mapK returns a SignallingRef instead of a Signal ... because we have two methods with the same name, I'm not entirely sure how they get resolved.

[rahulrangers]

I'm note entirely sure how they get resolved.

I think it is resolved as SignallingRef's mapK has an extra implicit parameter making it different from Signal’s mapK.

[armanbilge]

It does seem to be working!

I think it is resolved as SignallingRef's mapK has an extra implicit parameter making it different from Signal’s mapK.

That's right, they are different. I am just not sure how the compiler decides which method to choose when it's ambiguous.

[armanbilge]

nice work, thank you!