Error when providing instance that has Dagger multibinding dependency

Question

I'm getting an error when I run the following code. I'm attempting to inject a map constructed using Dagger multibinding into an instance of D via an @Provides method.

The error is:

error: [Dagger/MissingBinding] java.util.Map<java.lang.Class<dagger.A>,java.lang.String> cannot be provided without an @Provides-annotated method.
public abstract dagger.D d();
                         ^
  java.util.Map<java.lang.Class<dagger.A>,java.lang.String> is injected at
      dagger.ModuleA.provideD(map)
  dagger.D is provided at
      dagger.ComponentA.d()

The code is:

open class A
class B : A()
class C : A()
data class D(val map: Map<Class<A>, String>)

@Module
object ModuleA {

    @JvmStatic
    @Provides
    @IntoMap()
    @ClassKey(B::class)
    fun provideB(): String {
        return "B"
    }

    @JvmStatic
    @Provides
    @IntoMap()
    @ClassKey(C::class)
    fun provideC(): String {
        return "C"
    }

    @JvmStatic
    @Provides
    fun provideD(map: Map<Class<A>, String>): D {
        return D(map)
    }
}

@Component(modules = [ModuleA::class])
@Singleton
interface ComponentA {
    fun d(): D
}

fun main(args : Array<String>) {
    val dagger = DaggerComponentA.builder().build()
    println(dagger.d())
}

I can't find any direct examples of this. I only find examples that use field injection of the map itself.

Is what I'm attempting supported?

Answer 1

I figured it out:

open class A
class B : A()
class C : A()
data class D(val map: Map<Class<out A>, String>)

@MapKey
internal annotation class MyClassKey(val value: KClass<out A>)

@Module
object ModuleA {

    @JvmStatic
    @Provides
    @IntoMap()
    @MyClassKey(B::class)
    fun provideB(): String {
        return "B"
    }

    @JvmStatic
    @Provides
    @IntoMap()
    @MyClassKey(C::class)
    fun provideC(): String {
        return "C"
    }

    @JvmStatic
    @Provides
    @IntoMap()
    @MyClassKey(A::class)
    fun provideA(): String {
        return "A"
    }

    @JvmStatic
    @Provides
    fun provideD(map: Map<Class<out A>, String>): D {
        return D(map)
    }
}

@Component(modules = [ModuleA::class])
@Singleton
interface ComponentA {
    fun d(): D
}

fun main(args : Array<String>) {
    val dagger = DaggerComponentA.builder().build()
    val d = dagger.d()
    println(d.map) // {class dagger.B=B, class dagger.C=C, class dagger.A=A}
}

I needed to supply a custom @MapKey annotation:

@MapKey
internal annotation class MyClassKey(val value: KClass<out A>)

And change

fun provideD(map: Map<Class<A>, String>): D { 

to

fun provideD(map: Map<Class<out A>, String>): D {