Can I formulate ```fun Provider lt out Task gt generateCheck kotlinlang #getting-started

05/09/2022, 6:10 PM

Can I formulate

fun Provider<out Task>.generateChecksums(destination: Directory? = null) {
    get().generateChecksums(destination)
}

fun Task.generateChecksums(destination: Directory? = null) {
}

fun FileSystemLocation.generateChecksums(destination: Directory? = null) {
}

somehow so that the first one can work for both

Task

FileSystemLocation

? Just adding another method does not work of course as both would have the same type-erased form unless I call it differently.

05/09/2022, 6:52 PM

Can you add an interface which both

Task

FileSystem

05/09/2022, 7:15 PM

They are 3rd party classes

Best I could come up with while still missing explicit union types is

fun Provider<out Any>.generateChecksums(destination: Directory? = null) {
    when (val value = get()) {
        is Task -> value.generateChecksums(destination)
        is FileSystemLocation -> value.generateChecksums(destination)
        else -> error("Unsupported Type")
    }
}

but that's bad of course due to the method being callable on all providers. I hoped there is maybe some way using implicit union types.

05/09/2022, 7:55 PM

@JvmName("generateChecksumsTaskProvider")
public fun Provider<out Task>.generateChecksums()

@JvmName("generateChecksumsFileSystemLocationProvider")
public fun Provider<out FileSystemLocation>.generateChecksums()

will both appear as

.generateChecksums()

to Kotlin code

05/09/2022, 8:00 PM

Ah, nice, thanks. Will try that.

05/09/2022, 8:56 PM

come to think of it,

TaskProvider<out Task>

wouldn't have any JVM signature conflicts

05/10/2022, 7:46 AM

How would that help? Then I couldn't call it on

Provider<out Task>

. Besides that there are 5 more types to cover.

05/10/2022, 8:03 AM

do you really need an extension on

Provider<out Task>

tasks.register()

gives you a more specific subtype?

05/10/2022, 8:06 AM

Yes. And as I said, there are also 5 more types to cover. I just reduced it to two for the question.

Works perfectly fine now with the JvmName trick, thanks again