Given the following sealed class definition and `Flow` operator chain: ```sealed class LoadRequest&l...

# getting-started

[tseisel]

Given the following sealed class definition and Flow operator chain:

sealed class LoadRequest<out T> {
  object Pending : LoadRequest<Nothing>()
  class Success<T>(val data: T) : LoadRequest<T>()
  class Failure(val error: Exception) : LoadRequest<Nothing>()
}

val someFlow: Flow<Foo> = ...
val requestFlow: Flow<LoadRequest<Foo>> = someFlow
  .map { LoadRequest.Success(it) as LoadRequest<Foo> }
  .onStart { emit(LoadRequest.Pending) }
  .catch { emit(LoadRequest.Failure(it) }

The as LoadRequest<Foo> part is marked as No cast needed, but if I remove it then I get Type mismatch on LoadRequest.Pending and LoadRequest.Failure (it expects a LoadRequest.Success<Foo>).
Is it a compiler bug or is there a workaround ? I'd expect the compiler to figure out the proper type by analyzing the whole operator chain.

[dmitriy.novozhilov]

Inference of call chains is unsupported (it's very complex feature): https://youtrack.jetbrains.com/issue/KT-17115

As a workaround for removing warnings you can specify type parameter of `map`: map<LoadRequest<Foo>, LoadRequest<Foo>> { LoadRequest.Success(it) } or just suppress warning with @Suppress("USELESS_CAST")