Support Kotlin higher-order functions/lambdas

NativeScript supports marshalling Java bytecode generated by Kotlin. But Kotlin has a way to specify that a function takes another function in a much better way than Java.

Like this:

fun myfun(callback: (arg: String) -> Void)

It compiles to something like

public final void myfun(@org.jetbrains.annotations.NotNull final kotlin.jvm.functions.Function1<? super String, Void> callback)

where Function1 is a class containing an invoke method. Depending on how many args the function takes, it'll be called Function2, Function3 and so on.

Interacting with myfun from JavaScript would be done this way:

myfun(new kotlin.jvm.functions.Function1({ invoke: () => console.log("invoked") }))

It would be so cool if NativeScript supported Kotlin-functions out of the box, so the callback wouldn't need to be wrapped in FunctionX and myfun could be run via myfun(() => console.log("invoked")). This would make it easier to align with an Objective-C library, where blocks are supported.

To support Kotlin, my app.gradle currently looks like this:

buildscript {
    repositories {
        google()
        jcenter()
    }
    dependencies {
        classpath 'com.android.tools.build:gradle:2.3.3'
        classpath "org.jetbrains.kotlin:kotlin-gradle-plugin:1.2.30"
    }
}

dependencies {
  compile fileTree(dir: "libs", include: ["*.jar"])
  compile "org.jetbrains.kotlin:kotlin-stdlib-jre7:1.2.30"
}

android {  
  defaultConfig {  
    generatedDensities = []
    applicationId = "org.nativescript.test"  
  }  
  aaptOptions {  
    additionalParameters "--no-version-vectors"  
  }  
} 

No se nombran archivos ni pruebas del repositorio. Empieza por rastrear el marshalling del bytecode Java de NativeScript Android y cómo se representan kotlin.jvm.functions.Function1, Function2 y las aridades superiores; compáralo con la ruta existente de wrapping de callbacks de JavaScript. La tarea estará completada cuando los parámetros de funciones Kotlin puedan recibir callbacks de JavaScript directamente sin construir manualmente instancias de FunctionX.