I just learned about Kotlin's `where`, and that so...

# arrow

[CLOVIS]

I just learned about Kotlin's where, and that sounds so much perfect for combining typeclasses
https://kotlinlang.org/docs/reference/generics.html#upper-bounds

[bloder]

Yeah I'm using it in my project arch

suspend fun <T, R, M> T.fetchMapping(): M where T : Repository<R>, T : Mapper<R, M> = load().mapToValue()

class FetchUserUseCase(
  private val repository: Repository<User>,
  private val mapper: Mapper<UserPayload, User>
) : Repository<User> by repository, Mapper<UserPayload, User> by mapper

...

fetchUserUseCase.fetchMapping()

[pakoito]

https://arrow-kt.io/docs/patterns/dependency_injection/#composing-dependencies

[pakoito]

😄

[CLOVIS]

Wow, I really like the ‘creating impossible types' thing. When reading KEEP-87, I always thought there would need to be a specific syntax for it, I didn't notice Kotlin already has one 😅