I'm getting an error when trying to override a function that's implemented by delegation (context in...

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[daphillips]

I'm getting an error when trying to override a function that's implemented by delegation (context in thread)

[daphillips]

Here's what I'm trying to do:

private val cache: LoadingCache<Long, String> = Caffeine.newBuilder()
    .build { it.toString() }

object Foo: LoadingCache<Long, String> by cache {
    override fun get(key: Long): String {
        return cache.get(key)!!
    }
}

The error I get is:

Platform declaration clash: The following declarations have the same JVM signature (get(Ljava/lang/Object;)Ljava/lang/Object;): 
public open fun get(key: Long): String? defined in Foo
public open fun get(key: Long): String defined in Foo

The interface is a part of the caffeine cache library (written in Java). The relevant declaration is:

public interface LoadingCache<K, V> extends Cache<K, V> {
  @Nullable
  V get(@NonNull K key);
}

Is there something that I'm doing wrong?

[daphillips]

Also, if I change the return type of the overrided function from String to String? I get the same Platform declaration clash error

[Brett Best]

override fun get(key: Long): String? {

[Brett Best]

Ah 🤔

[daphillips]

same if i drop override from the non-null return type

[edrd]

Check this: https://kotlinlang.org/docs/reference/java-to-kotlin-interop.html#handling-signature-clashes-with-jvmname

[edrd]

Not sure it works with override, though

[daphillips]

'@JvmName' annotation is not applicable to this declaration ¯\_(ツ)_/¯

[edrd]

I think that's one reason why some people don't like the implementation by delegation feature 😛

[edrd]

Well, apparently the only way is to use delegation with manual calls to cache

[daphillips]

Oh interesting. I didn't realize that people didn't really like it. Haven't used it much though.

[daphillips]

And yeah I discovered that too. I ended up just working with the cache instance directly; all I wanted to do was try to make it non-null but going through all the trouble to get it there didn't outweigh just handling it where I call get