this code doesn’t complain in compilation time but in runtime if I don’t specify the type of

classLoaders: Array<out ClassLoader>?

when

*classLoaders

is passed as parameter

val classLoaders = reflections.configuration.classLoaders // Array<out ClassLoader>?
ReflectionUtils.forNames<Any>(reflections.allTypes, *classLoaders)

What does it say at runtime?

NPE

When you are interacting with platform code that has no Nullable annotations, Kotlin lets you decide whether the type is nullable or not and when you don’t do that it decides based on context.

And this is why we should never promote Kotlin as a null-safe language because it's only as null-safe as it's platform i.e. not at all.

well, safety is relative. You can always do unsafe things like using platform types or casting, but outside of that you are pretty much safe.

@poohbar as long as you stay withing Kotlin it's pretty much null-safe.

stay withing Kotlin

How many real-world projects can get away with not using Java?

actually

reflections.configuration.classLoaders

is annotated with a

@javax.annotation.Nullable

return type, I thought this could be inferred.

thank you @pavel

@poohbar only use nullable types when interfacing with java and you have full null-safety

Since the compiler does not force you to do that it's like saying that Java is null-safe if you do a null check before accessing any reference.

at one point, kotlin did exactly that, but it was removed because a lot of developers were not happy with it

I know the history of Kotlin. And I also know that once this was removed Kotlin ceased to be a null-safe language and we should stop saying it is.

Kotlin is null-safe, the interaction with Java is not. Do you also say that Java is not memory safe because it can interact with the JNI?