Property delegates not working in custom Gradle tasks

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1

I have the following simple custom task with a custom property delegate:

import kotlin.reflect.KProperty

class MyDelegate<T : Any>(val default: T) {
    var curVal = default

    operator fun getValue(thisRef: Any?, property: KProperty<*>): T {
        return curVal
    }

    operator fun setValue(thisRef: Any?, property: KProperty<*>, value: T) {
        curVal = value
    }
}

class MyTask : DefaultTask() {
    @get:Internal
    var x by MyDelegate("XXXXXX")

    @TaskAction
    fun run() {
        println("hello")
    }
}

val mytask by tasks.registering(MyTask::class) {
}

But when I try to run the task, it fails with the following error:

$ gradle mytask
[...]
Script compilation errors:

  Line 17:     var x by MyDelegate("XXXXXX")
                        ^ Type 'TypeVariable(T)' has no method 'getValue(Build_gradle.MyTask, KProperty<*>)' and thus it cannot serve as a delegate

  Line 17:     var x by MyDelegate("XXXXXX")
                        ^ Type 'TypeVariable(T)' has no method 'setValue(Build_gradle.MyTask, KProperty<*>, [ERROR : Type from delegate])' and thus it cannot serve as a delegate for var (read-write property)

On the other hand, the following Kotlin script file is executed by kotlinc without any issues:

$ cat test.kts
import kotlin.reflect.KProperty

class MyDelegate<T : Any>(val default: T) {
    var curVal = default

    operator fun getValue(thisRef: Any?, property: KProperty<*>): T {
        return curVal
    }

    operator fun setValue(thisRef: Any?, property: KProperty<*>, value: T) {
        curVal = value
    }
}

class MyTask {
    var x by MyDelegate("XXXXXX")

    fun run() {
        println("hello")
    }
}

val t = MyTask()
println(t.x)
t.run()
$ kotlinc -script test.kts
XXXXXX
hello

If I make thisRef be a generic type it works:

$ cat build.gradle.kts
import kotlin.reflect.KProperty

class MyDelegate<T : Any, S : Any>(val default: T) {
    var curVal = default

    operator fun getValue(thisRef: S?, property: KProperty<*>): T {
        return curVal
    }

    operator fun setValue(thisRef: S?, property: KProperty<*>, value: T) {
        curVal = value 
    }
}
 
open class MyTask : DefaultTask() {
    @get:Internal
    var x by MyDelegate<String, MyTask>("XXXXXX")

    @TaskAction
    fun run() {
        println("hello")
    }
}

val mytask by tasks.registering(MyTask::class) {
}
$ gradle mytask

> Task :mytask
hello

BUILD SUCCESSFUL in 346ms
1 actionable task: 1 executed

But it’s annoying to have to manually specify the types in MyDelegate<String, MyTask>, since MyTask can’t be inferred by Kotlin.

Is it possible make this work somehow?