Why doesn’t kotlin serialization complain about the interface not being serializable here?

# serialization

[Paul Woitaschek]

Why doesn’t kotlin serialization complain about the interface not being serializable here?

[Paul Woitaschek]

Code for those who can’t see images:

@Serializable
data class SerializableSomething(
  val i: SomeInterface,
  val b: SomeClass, <- error here
)

interface SomeInterface

class SomeClass

[Paul Woitaschek]

Background: we just had a crash where a sealed interface was not marked as Serializable and relied upon that kotlinx usually fails the compilation if a type is not serializable

[Adam S]

https://github.com/Kotlin/kotlinx.serialization/blob/master/docs/polymorphism.md#serializing-interfaces

all interfaces are considered to be implicitly serializable with the PolymorphicSerializer strategy

here’s a relevant bit from the docs, but I’m not sure if it might help!

[Paul Woitaschek]

Uh dang. That takes a big portion of the compiler time safety away

[Paul Woitaschek]

I really want to disable that behavior

[Adam S]

if it was disabled, what serializer would you use for SomeInterface?

[Paul Woitaschek]

Either the generated serializer if it's marked with Serializable or the one specified in Serializable(with)