interfacedef's method() generates strange signature for a nullable return type

[ForNeVeR]

I want to specify an interface with a method that has a nullable return type.

var IMyInterface = interfacedef("IMyInterface") {
     method("get", PredefinedType.string.nullable)
}

But it generates to:

interface IMyInterface
{
    fun get() : StringNullable
}

I expected fun get() : String?

Originally posted by @al-darmonski in #206 (comment)