IssueTracker

AGP: 8.2.2 (also reproducible on 8.6.1)

R8: 8.2.47 (also reproducible on 8.7.14 and 8.8.7-dev), reproducible in both full and compat modes.

Kotlin: 1.9.23 (also reproducible on 2.0.0 and 2.0.20)

I encounter an issue with incorrect optimization of kotlin interface default method (with jvm-default=all compiler option) when classes that implement the interface have common base class. It's reproducible with java interface default method as well.

Example:

Interface:

interface TestInterface {
    fun foo() {
        println("foo")
    }
}

Interface caller:

import android.content.Context
import android.os.Bundle
import androidx.fragment.app.Fragment

class TestFragment : Fragment() {

    private var testInterface: TestInterface? = null

    override fun onAttach(context: Context) {
        super.onAttach(context)
        testInterface = context as? TestInterface
    }

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        testInterface?.foo()
    }
}

First impl class (doesn't override default implementation from interface):

import android.os.Bundle
import androidx.appcompat.app.AppCompatActivity

class FirstActivity : AppCompatActivity(), TestInterface {

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        if (savedInstanceState == null) {
            supportFragmentManager.beginTransaction().add(TestFragment(), "test").commit()
        }
    }
}

Second impl class (overrides default implementation from interface by calling method finish() available in common base class):

import androidx.activity.ComponentActivity

class SecondActivity : ComponentActivity(), TestInterface {

    override fun foo() {
        finish()
    }
}

Optimizer moves foo() method implementation from SecondActivity to androidx.core.app.ComponentActivity:

.method public foo()V
    .registers 1

    .line 1
    invoke-virtual {p0}, Landroidx/core/app/ComponentActivity;->finish()V

    .line 2
    .line 3
    .line 4
    return-void
.end method

but it doesn't add default implementation from TestInterface to FirstActivity. This way FirstActivity will be incorrectly finished when the interface method is called.

Test application to reproduce the issue is attached.