I'm running into a weird problem recently in Andro...

# arrow

[Lukasz Kalnik]

I'm running into a weird problem recently in Android Studio Electric Eel. All of a sudden, the bind() function of the either {} scope stops being recognized (although it just worked a few moments before and there were no changes in the code):

Unresolved reference. None of the following candidates is applicable because of receiver type mismatch: 
public open suspend fun <B> Either<CallError, TypeVariable(B)>.bind(): TypeVariable(B) defined in arrow.core.continuations.EffectScope
public open suspend fun <B> Option<TypeVariable(B)>.bind(shift: () -> CallError): TypeVariable(B) defined in arrow.core.continuations.EffectScope
public open suspend fun <B> Validated<CallError, TypeVariable(B)>.bind(): TypeVariable(B) defined in arrow.core.continuations.EffectScope
public open suspend fun <B> EagerEffect<CallError, TypeVariable(B)>.bind(): TypeVariable(B) defined in arrow.core.continuations.EffectScope
public open suspend fun <B> Effect<CallError, TypeVariable(B)>.bind(): TypeVariable(B) defined in arrow.core.continuations.EffectScope
public open suspend fun <B> Result<TypeVariable(B)>.bind(transform: (Throwable) -> CallError): TypeVariable(B) defined in arrow.core.continuations.EffectScope

[Lukasz Kalnik]

scenesRepository.scenes.value is of type Either<DataMissing, List<Scene>>

[simon.vergauwen]

is DataMissing a subtype of CallError ?

[Lukasz Kalnik]

Oh yes, that might be the problem 🤦

[Lukasz Kalnik]

I have a mix of functions inside the either scope returning different types of errors which are not related...

[Lukasz Kalnik]

Thanks!

[simon.vergauwen]

My pleasure Lukasz ☺️

[Lukasz Kalnik]

I wish there was a more telling error message, but I suppose that's not easy.

[simon.vergauwen]

I don't even think we can provide a custom error message for that 🤔 That would be pretty cool though!

Curious if you could somehow leverage @Deprecation with DeprecationLevel.ERROR for that. Going to give that a try, that would be really awesome.

[Lukasz Kalnik]

Also the strange thing is that it actually built before and I didn't change a single line

[Lukasz Kalnik]

Maybe that's a bug in the compiler type inference

[simon.vergauwen]

Curious 🤔

[simon.vergauwen]

It's actually possible to use @Deprecation for this 😮

[Lukasz Kalnik]

Wow, that's really interesting!

[Lukasz Kalnik]

Feels a bit like a hack though ;)

[simon.vergauwen]

If we can figure out a good error message, then we should probably leverage this in Arrow. Too bad we cannot reference the actual E and R types.

Yes, it's definitely a bit of a hack but it has some cool use-cases.

[simon.vergauwen]

Yesterday I also shared this on Twitter, https://github.com/LouisCAD/Splitties/blob/ca6218a511eec8f59620b40894fe1c47a64555d[…]coroutines/src/commonMain/kotlin/splitties/coroutines/Racing.kt

[Lukasz Kalnik]

To be precise it should say with the same Left type or subtype

[simon.vergauwen]

Going to let this sink in for a while 😄 I'd love to provide better support for Arrow in IDEA, but wish this was possible through the language rather than building an IDEA plugin.

[simon.vergauwen]

I.e. we're planning to leverage @DslMarker more, and have been able to convert some comples Resource structures into simple DSLs without compromising correctness.

[Stylianos Gakis]

https://twitter.com/vergauwen_simon/status/1578047840227557379?t=x9Clw3QEa1UEhTRm3CDYvw&s=19
Slack-and-twitter-driven development going on over here 😅

[simon.vergauwen]

💪 Arrow is a community effort, combining everyones feedback has been key to what it is today. Kotlin community is really awesome 🙌