Basics #5: Some things can't be constructor-injected. What is the solution?

explanation.md

From the Hilt-Android docs:

Sometimes a type cannot be constructor-injected. This can happen for multiple reasons. For example, you cannot constructor-inject an interface. You also cannot constructor-inject a type that you do not own, such as a class from an external library. In these cases, you can provide Hilt with binding information by using Hilt modules.

source: Hilt Modules

Not being able to constructor inject an interface is shown in the example below. Not being able to inject a class that you do not own can't even be shown in an example. You just can't do it because you can't even annotate the class with @Inject. It's impossible because you don't have access to it.

MainActivity.kt

import androidx.appcompat.app.AppCompatActivity
import android.os.Bundle
import androidx.fragment.app.Fragment
import dagger.hilt.android.AndroidEntryPoint
import javax.inject.Inject

@AndroidEntryPoint
class MainActivity : AppCompatActivity() {

    @Inject
    lateinit var someClass: SomeClass

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)

        println(someClass.doAThing())
    }
}

class SomeClass
@Inject
constructor(
    private val someInterfaceImpl: SomeInterface
){
    fun doAThing(): String{
        return "Look I got: ${someInterfaceImpl.getAThing()}"
    }
}

class SomeInterfaceImpl
@Inject
constructor(): SomeInterface {
    override fun getAThing() : String{
        return "A Thing"
    }
}

interface SomeInterface{
    fun getAThing(): String
}