Annotations: when is arrayOf needed

Question

Lets say we have a Java annotation as follows:

@Target(ElementType.METHOD)
@Retention(RetentionPolicy.RUNTIME)
@Documented
public @interface Hans {
    String[] value() default {};
}

In Kotlin I am allowed to use the Annotation as follows:

@Hans(value = "test")

As soon as i change the property name from 'value' to 'name' it is not allowed to use this syntax anymore, instead I need to have arrayOf(..).

@Hans(name = arrayOf("test"))

Is that a bug or a design decision and if so what is the reason behind it.

Many thanks in advance Kind regards

Answer 1

No, this is not a bug. Java treats the value annotation specially and allows to omit the annotation parameter name when you use it. Kotlin follows this special treatment and also allows you to omit the parameter name, allowing you to write @Hans("test"). Supporting this syntax for array parameters requires to treat the parameter as vararg, so Kotlin does that and allows you to omit the arrayOf.