AGP: 8.5.1

R8: 8.5.27

Kotlin: 2.0.0

I create an SDK for other apps to consume, and I started to see crashes around fun interfaces, when consumers compile with full mode enabled.

Source:

class MainActivity : Activity() {
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        hello()
    }
}

fun interface FunInterface1 {
    fun doBusiness()
}

fun interface FunInterface2 {
    fun startTheShow()
}

fun hello() {
    val instance1 = FunInterface1 { println("Doing business") }
    val instance2 = FunInterface2 { println("Starting the show") }
    check(instance1::class.java != instance2::class.java)
}

When running this code in debug, no crash occurs. When running this code in release with minify and fullmode, it crashes, because classes are merged.

These fun interfaces are compiled by kotlin to invokedynamic:

 0: invokedynamic #22,  0             // InvokeDynamic #0:doBusiness:()Lcom/example/r8/FunInterface1;
 5: astore_0
 6: invokedynamic #30,  0             // InvokeDynamic #1:startTheShow:()Lcom/example/r8/FunInterface2;
11: astore_1
12: aload_0
13: invokevirtual #34                 // Method java/lang/Object.getClass:()Ljava/lang/Class;
16: aload_1
17: invokevirtual #34                 // Method java/lang/Object.getClass:()Ljava/lang/Class;

Then, as I understand, R8 rewrites calls to invokedynamic to instantiation of R8-generated synthetic classes, then R8 merges these two classes into one because they are synthetic.

If I rewrite these SAM declarations to anonymous objects, kotlin compiles them to lambda classes (MainActivityKt$hello$instance1$1), and release mode does not crash

fun hello() {
    val instance1 = object : FunInterface1 {
        override fun doBusiness() {
            println("Doing business")
        }
    }
    val instance2 = object : FunInterface2 {
        override fun startTheShow() {
            println("Starting the show")
        }
    }
    check(instance1::class.java != instance2::class.java)
}

I also attached sample.

Is this a bug?

If not, how can I disable horizontal class merging for my classes?

Issue 356896482

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