Generic confusion

1

 

Error:(24, 29) Kotlin: Type inference failed: Cannot infer type parameter T in fun <T : net.unitcraft.game.HasName> name(tp: java.lang.Class<T>): kotlin.String

None of the following substitutions

(java.lang.Class<net.unitcraft.game.EntityAbs>)

(java.lang.Class<net.unitcraft.game.HasName>)

(java.lang.Class<kotlin.Nothing>)

can be applied to

(java.lang.Class<out net.unitcraft.game.EntityAbs>)


What is means? How to write properly?

2

I make errs in previous post.

class TestHasName {
    Test fun testName() {
        val all = listOf(javaClass<EntityTest>(),javaClass<EntityTest2>())
        for(tp in all) {
            println(Name.name(tp)) // this dont compiles
        }
    }
}



abstract class EntityAbs : Name


class EntityTest:EntityAbs()


class EntityTest2:EntityAbs()


trait Name {

  fun name(): String = Name.name(javaClass)


  class object {

  fun <T : Name> name(tp: Class<T>) = tp.getSimpleName()

  }

}


Compiler message:

Error:(24, 26) Kotlin: Type inference failed: Cannot infer type parameter T in fun <T : net.unitcraft.game.Name> name(tp: java.lang.Class<T>): kotlin.String

None of the following substitutions

(java.lang.Class<net.unitcraft.game.EntityAbs>)

(java.lang.Class<net.unitcraft.game.Name>)

(java.lang.Class<kotlin.Nothing>)

can be applied to

(java.lang.Class<out net.unitcraft.game.EntityAbs>)


How to write this without compile err?

3

To fix Name.name read http://kotlinlang.org/docs/reference/generics.html#variance

4

I reasked my question with more details: http://devnet.jetbrains.com/thread/457013