error: [Dagger/DependencyCycle] Found a dependency cycle with Dagger2

Question

I am trying to use @BindsInstance in a Component Builder, but can't inject dependency into a module

That is the component:

@Component(modules = [MainModule::class])
interface MainComponent {
    fun inject(activity: MainActivity)

    @Component.Builder
    interface Builder {
        @BindsInstance
        fun mainDep(dep: MainTest): Builder

        fun build(): MainComponent
    }
}

That is the module:

@Module
class MainModule {

    @Provides
    fun provideMainTest(mainTest: MainTest) = mainTest
}

That is the class to inject:

interface MainTest {
    fun mainTest()
}

class MainTestImpl: MainTest {
    override fun mainTest() {
        println("main test")
    }
}

But when I try to inject it into MainActivity I get a compiler error

error: [Dagger/DependencyCycle] Found a dependency cycle:
public abstract interface MainComponent {
                ^
      com.example.testdagger.di.MainTest is injected at
          com.example.testdagger.di.MainModule.provideMainTest(mainTest)
      com.example.testdagger.di.MainTest is injected at
          com.example.testdagger.di.MainModule.provideMainTest(mainTest)

Answer 1

Can you try and say what will happen like this:

    @BindsInstance
    fun mainDep(dep: MainTestImpl): Builder

and also:

@Module
class MainModule {

    @Provides
    fun provideMainTest(mainTestImpl: MainTestImpl): MainTest = mainTestImpl
}

I know that it is not exactly what you want to achieve, but I want to check the result. Also, please provide how you create the component and how do you inject the Activity.