Error for project.tasks.getting delegation in .kt file, but not in build.gradle.kts

Help/Discuss
1

The Kotlin function below compiles fine when in build.gradle.kts and can be used in that file.

The same function in a normal .kt file, however, outputs a compile error for the line with the comment // ERROR HERE.

Is it possible to fix this? If so, how?

// Imports only in .kt file, not in build.gradle.kts
import org.gradle.api.Task
import org.gradle.kotlin.dsl.getting

val Task.isTestCompile: Boolean
    get() {
        val testClasses by project.tasks.getting // ERROR HERE

        return testClasses.taskDependencies.getDependencies(testClasses).contains(this)
    }

The command-line gradlew error is:

Missing 'getValue(Nothing?, KProperty<*>)' method on delegate of type 'ExistingDomainObjectDelegate<out Task!>'

In IntelliJ 2019.3 Beta, the error is:

Type 'ExistingDomainObjectDelegate<out Task!>' has no method 'getValue(Nothing?, KProperty<*>)' and thus it cannot serve as a delegate
2

Have you found the root cause of this? I have the same problem with sourceSets after upgrading to Kotlin 1.3.70

3

I just replaced the error line with the following less elegant line:

val testClasses = project.tasks.getByName("testClasses")
4

Adding {} also worked for me:

    val testClasses: Task  by getting {}