Do the types in kotlin.collections implement any o...

# getting-started

[Matthew Hall]

Do the types in kotlin.collections implement any of the java.lang or java.util interfaces on the JVM? e.g. java.util.List, java.lang.Iterable

[karelpeeters]

Here are the mappings: https://kotlinlang.org/docs/reference/java-interop.html#mapped-types

[karelpeeters]

There's some magic to it but yes, Kotlin's List implements Iteratable and they're both mapped to the respective Java type.

[fred.deschenes]

@Matthew Hall: I'm guessing you're asking for this issue : https://github.com/jdbi/jdbi/issues/1482?

[Matthew Hall]

correct

[karelpeeters]

Could you give some context? What exactly is going on in that issue?

[araqnid]

List<E> (E : Enum<E>) is being mapped to java.util.List<? extends E> and it looks like jdbi doesn’t handle that

[araqnid]

Kotlin adds the wildcard because it sees List as immutable and hence the E is an “out” parameter. imho it’s doing the right thing, and jdbi should just trim the wildcard to its upper bound

[araqnid]

the JvmSuppressWildcard annotation works too, that’s what I used for Guice

[araqnid]

well, except that Enum classes in Java are final if their values don’t actually override anything ..

[karelpeeters]

I see, that's a lot of things coming together!

[Matthew Hall]

I believe we've found a workaround for the current use case: when the type variable extends Enum, we get the erased type--which for an out MyEnum type variable just gives MyEnum.class.

[Matthew Hall]

We might have to give thought to whether it is legitimate for us to reduce ? extends Foo to just Foo for our use case