abstract class A : DefaultTask() {
    
    @get:InputFile
    val from: Property<java.nio.file.Path> = project.objects.property<java.nio.file.Path>()

    @get:OutputFile
    val into: Property<java.nio.file.Path> = project.objects.property<java.nio.file.Path>()

    @TaskAction
    fun foo() {
        into.get().toFile().writeText(from.get().toFile().readText())
    }
}

abstract class B : DefaultTask() {

    @get:InputFile
    abstract val from: RegularFileProperty

    @get:OutputFile
    abstract val into: RegularFileProperty

    @TaskAction
    fun foo() {
        val fromFile = from.asFile.get()
        check(fromFile.exists())
        into.get().asFile.writeText(fromFile.readText())
    }
}

val aTask = tasks.register<A>("foo") {
    from.set(layout.projectDirectory.file("foo.txt").asFile.toPath())
    into.set(layout.buildDirectory.file("bar.txt").get().asFile.toPath())
}

val b = tasks.register<A>("bar") {
    from.set(aTask.flatMap { it.into })
    into.set(layout.buildDirectory.file("baz.txt").get().asFile.toPath())
}